UNDERWRITING AGREEMENT

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Exhibit 1.1

$80,000,000

FRONTIER AIRLINES, INC.

5% CONVERTIBLE DEBENTURES DUE 2025

UNDERWRITING AGREEMENT

December 1, 2005

        December 1, 2005

Morgan Stanley & Co. Incorporated
Citigroup Global Markets Inc.

c/o

Morgan Stanley & Co. Incorporated
1585 Broadway
New York, New York 10036

Dear Sirs and Mesdames:

         Frontier Airlines, Inc. , a Colorado corporation (the " Company "), proposes to issue and sell to the several Underwriters named in Schedule II hereto (the " Underwriters ") $80,000,000 principal amount of its 5% Convertible Debentures due 2025 (the " Firm Securities ") to be issued pursuant to the provisions of an indenture to be dated as of December 7, 2005 and a supplemental indenture (together the " Indenture ") between the Company and U.S. Bank National Association, as Trustee (the " Trustee "). The Company also proposes to issue and sell to the several Underwriters not more than an additional $12,000,000 principal amount of its 5% Convertible Debentures due 2025 (the " Additional Securities ") if and to the extent that you, as Managers of the offering, shall have determined to exercise, on behalf of the Underwriters, the right to purchase such 5% Convertible Debentures due 2025 granted to the Underwriters in Section 2 hereof. The Firm Securities and Additional Securities are hereinafter collectively referred to as the " Securities ". The Securities will be convertible into shares of common stock (the " Common Stock "), no par value per share, of the Company (the " Underlying Securities ").

        The Company has filed with the Securities and Exchange Commission (the " Commission ") a registration statement, including a prospectus, (the file number of which is set forth in Schedule I hereto) on Form S-3, relating to certain of its debt and equity securities (the " Shelf Securities "), including the Securities, to be issued from time to time by the Company. The registration statement as amended to the date of this Agreement, including the information (if any) deemed to be part of the registration statement at the time of effectiveness pursuant to Rule 430A or Rule 430B under the Securities Act of 1933, as amended (the " Securities Act "), is hereinafter referred to as the " Registration Statement, " and the related prospectus covering the Shelf Securities dated November 25, 2005 in the form first used to confirm sales of the Securities (or in the form first made available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the " Basic Prospectus ." The Basic Prospectus, as supplemented by the prospectus supplement specifically relating to the Securities in the form first used to confirm sales of the Securities (or in the form first made available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the " Prospectus ," and the term " preliminary prospectus " means any preliminary form of the Prospectus. For purposes of this Agreement, " free writing prospectus " has the meaning set forth in Rule 405 under the Securities Act and " Time of Sale Prospectus " means the preliminary prospectus, together with the free writing prospectuses, if any, each identified in Schedule I hereto. As used herein, the terms "Registration Statement," "Basic Prospectus," "preliminary prospectus," "Time of Sale Prospectus" and Prospectus shall include the documents, if any, incorporated by reference therein. The terms " supplement ," " amendment ," and " amend " as used herein with respect to the Registration Statement, the Basic Prospectus, the Time of Sale Prospectus, any preliminary prospectus or free writing prospectus shall include all documents subsequently filed by the Company with the Commission pursuant to the Securities Exchange Act of 1934, as amended (the " Exchange Act "), that are deemed to be incorporated by reference therein.

        SECTION 1. Representations and Warranties . The Company represents and warrants to and agrees with each of the Underwriters that:

        (a)   The Registration Statement has become effective; no stop order suspending the effectiveness of the Registration Statement is in effect, and no proceedings for such purpose are pending before or, to the knowledge of the Company, threatened by the Commission.

        (b)   (i) Each document, if any, filed or to be filed pursuant to the Exchange Act and incorporated by reference in the Time of Sale Prospectus or the Prospectus complied or will comply when so filed in all material respects with the Exchange Act and the applicable rules and regulations of the Commission thereunder, (ii) each part of the Registration Statement, when such part became effective, did not contain, and each such part, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iii) the Registration Statement as of the date hereof does not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iv) the Registration Statement and the Prospectus comply, and as amended or supplemented, if applicable, will comply in all material respects with the Securities Act and the applicable rules and regulations of the Commission thereunder, (v) the Time of Sale Prospectus does not, and at the time of each sale of the Securities in connection with the offering and at the Closing Date (as defined in Section 4), the Time of Sale Prospectus, as then amended or supplemented by the Company, if applicable, will not, contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading and (vi) the Prospectus does not contain and, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the representations and warranties set forth in this paragraph do not apply to (A) statements or omissions in the Registration Statement, the Time of Sale Prospectus or the Prospectus based upon information relating to any Underwriter furnished to the Company in writing by such Underwriter through you expressly for use therein or (B) that part of the Registration Statement that constitutes the Statement of Eligibility (Form T-1) under the Trust Indenture Act of 1939, as amended (the " Trust Indenture Act "), of the Trustee.

        (c)   The Company is not an "ineligible issuer" in connection with the offering of the Securities pursuant to Rules 164, 405 and 433 under the Securities Act. Any free writing prospectus that the Company is required to file pursuant to Rule 433(d) under the Securities Act has been, or will be, filed with the Commission in accordance with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Each free writing prospectus that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or that was prepared by or behalf of or used or referred to by the Company complies or will comply in all material respects with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Except for the free writing prospectuses, if any, identified in Schedule I hereto, and electronic road shows each furnished to you before first use, the Company has not prepared, used or referred to, and will not, without your prior consent, prepare, use or refer to, any free writing prospectus.

        (d)   The Company has been duly incorporated, is validly existing as a corporation in good standing under the laws of the jurisdiction of its incorporation, has the corporate power and authority to own its property and to conduct its business as described in the Time of Sale Prospectus and is duly qualified to transact business and is in good standing in each jurisdiction in which the conduct of its business or its ownership or leasing of property requires such qualification, except to the extent that the failure to be so qualified or be in good standing would not have a material adverse effect on the Company. The Company has no existing subsidiaries.

        (e)   This Agreement has been duly authorized, executed and delivered by the Company.

        (f)    The authorized capital stock of the Company conforms as to legal matters to the description thereof contained in the Time of Sale Prospectus.

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        (g)   The shares of capital stock of the Company outstanding prior to the issuance of the Securities have been duly authorized and are validly issued, fully paid and non-assessable.

        (h)   The Securities have been duly authorized and, when executed and authenticated in accordance with the provisions of the Indenture and delivered to and paid for by the Underwriters in accordance with the terms of this Agreement, will be valid and binding obligations of the Company, enforceable in accordance with their terms, subject to the effects of applicable bankruptcy, insolvency and similar laws affecting creditors' rights generally and equitable principles of general applicability, and will be entitled to the benefits of the Indenture.

        (i)    The Underlying Securities issuable upon conversion of the Securities have been duly authorized and reserved and, when issued upon conversion of the Securities in accordance with the terms of the Securities, will be validly issued, fully paid and non-assessable, and the issuance of the Underlying Securities will not be subject to any preemptive or similar rights.

        (j)    The Indenture has been duly authorized, and on the Closing Date (as defined below) will be executed and delivered by, and a valid and binding agreement of, the Company, enforceable in accordance with its terms, subject to the effects of applicable bankruptcy, insolvency and similar laws affecting creditors' rights generally and equitable principles of general applicability, and the Indenture has been duly qualified under the Trust Indenture Act.

        (k)   The execution and delivery by the Company of, and the performance by the Company of its obligations under, this Agreement, the Indenture and the Securities will not contravene any provision of applicable law or the articles of incorporation or By-laws of the Company or any agreement or other instrument binding upon the Company that is material to the Company, or any judgment, order or decree of any governmental body, agency or court having jurisdiction over the Company, and no consent, approval, authorization or order of, or qualification with, any governmental body or agency is required for the performance by the Company of its obligations under this Agreement, the Indenture or the Securities, except such as have been obtained under the Securities Act and the Exchange Act, and except such as may be required by the securities or Blue Sky laws of the various states in connection with the offer and sale of the Securities.

        (l)    There has not occurred any material adverse change, or any development involving a prospective material adverse change, in the condition, financial or otherwise, or in the earnings, business or operations of the Company, from that set forth in the Time of Sale Prospectus (exclusive of any amendments or supplements thereto subsequent to the date of this Agreement).

        (m)  There are no legal or governmental proceedings pending or threatened to which the Company is a party or to which any of the properties of the Company is subject that are required to be described in the Registration Statement or the Prospectus and are not so described or any statutes, regulations, contracts or other documents that are required to be described in the Registration Statement or the Prospectus or to be filed as exhibits to the Registration Statement that are not described or filed as required. The Time of Sale Prospectus contains in all material respects the same description of the foregoing matters contained in the Prospectus.

        (n)   Each preliminary prospectus filed as part of the registration statement as originally filed or as part of any amendment thereto, or filed pursuant to Rule 424 under the Securities Act, complied when so filed in all material respects with the Securities Act and the applicable rules and regulations of the Commission thereunder.

        (o)   The Company is not, and after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the Prospectus will not be, required to register as an "investment company" as such term is defined in the Investment Company Act of 1940, as amended.

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        (p)   The Company (i) is in compliance with any and all applicable foreign, federal, state and local laws and regulations, judgments, orders or binding agreements relating to the protection of human health and safety, the environment or hazardous or toxic substances or wastes, pollutants or contaminants (" Environmental Laws "), (ii) has received all permits, licenses or other approvals required under applicable Environmental Laws to conduct its businesses and (iii) is in compliance with all terms and conditions of any such permit, license or approval, except where such noncompliance with Environmental Laws, failure to receive required permits, licenses or other approvals or failure to comply with the terms and conditions of such permits, licenses or approvals would not, singly or in the aggregate, have a material adverse effect on the Company.

        (q)   There are no costs or liabilities associated with Environmental Laws (including, without limitation, any fines or penalties, settlement or damage awards, or capital or operating expenditures required for clean-up, closure of properties or compliance with Environmental Laws or any permit, license or approval, any related constraints on operating activities and any potential liabilities to third parties) which would, singly or in the aggregate, have a material adverse effect on the Company.

        (r)   There are no contracts, agreements or understandings between the Company and any person granting such person the right to require the Company to file a registration statement under the Securities Act with respect to any securities of the Company (except as otherwise disclosed in the Registration Statement) or to require the Company to include such securities with the Securities registered pursuant to the Registration Statement.

        (s)   Subsequent to the date as of which information is given in the Time of Sale Prospectus, (i) the Company has not incurred any material liability or obligation, direct or contingent, or entered into any material transaction, in each case, not in the ordinary course of business or as described in or contemplated by the Prospectus; (ii) the Company has not purchased any of its outstanding capital stock, nor declared, paid or otherwise made any dividend or distribution of any kind on its capital stock; (iii) there has not been any material change in the capital stock, short-term debt or long-term debt of the Company except in each case as described in or contemplated by the Prospectus; and (iv) there has been no prohibition or suspension of the operation of the Company's aircraft, including as a result of action taken by the Federal Aviation Administration or the Department of Transportation.

        (t)    The Company has good and marketable title in fee simple to all real property and good and marketable title to all personal property owned by it which is material to the business of the Company, free and clear of all liens, encumbrances and defects except such as are described in the Time of Sale Prospectus or the Registration Statement or such as do not materially affect the value of such property or do not interfere with the use made and proposed to be made of such property by the Company; and any real property and buildings held under lease by the Company are held by it under valid, subsisting and enforceable leases with such exceptions as are not material and do not interfere with the use made and proposed to be made of such property and buildings by the Company, in each case except as described in or contemplated by the Time of Sale Prospectus.

        (u)   (i) The Company possesses such permits, licenses, approvals, consents and other authorizations (collectively " Government Licenses ") issued by the appropriate federal, state, local or foreign regulatory agencies or bodies, including the Department of Transportation, the Federal Aviation Administration or the Federal Communications Commission necessary to conduct the business now operated by it; (ii) the Company is in compliance with the terms and conditions of all such Governmental Licenses, except where the failure so to comply would not, singly or in the aggregate, have a material adverse effect on the Company; (iii) all of the Government Licenses are valid and in full force, except where the invalidity of such Governmental Licenses or the failure of

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such Governmental Licenses to be in full force and effect would not have a material adverse effect on the Company; and (iv) the Company has not received any notice of proceedings relating to the revocation or modification of any such Governmental Licenses which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would have a material adverse effect on the Company.

        (v)   Except as described in the Time of Sale Prospectus, no material labor dispute with the employees of the Company exists or, to the knowledge of the Company, is imminent; and the Company is not aware, but without any independent investigation or inquiry, of any existing, threatened or imminent labor disturbance by the employees of any of its principal suppliers, manufacturers or contractors that could have a material adverse effect on the Company.

        (w)  The Company is insured by insurers that the Company reasonably believes to be of recognized financial responsibility against such losses and risks and in such amounts as are customary in the businesses in which it is engaged; the Company has not been refused any insurance coverage sought or applied other than in connection with instances where the Company was seeking to obtain insurance coverage at more attractive rates; and the Company has no reason to believe that it will not be able to renew its existing insurance coverage as and when such coverage expires or to obtain similar coverage from similar insurers as may be necessary to continue its business at a cost that would not have a material adverse effect on the Company, except as described in or contemplated by the Time of Sale Prospectus.

        (x)   The Company maintains a system of internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management's general or specific authorizations in all material respects, (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles and to maintain asset accountability and (iii) regarding prevention or timely detection of unauthorized acquisition, use or disposition of the Company's assets that could have a material effect on the Company's financial statements. Except as described in or incorporated by reference into the Time of Sale Prospectus, since the most recent audit of the effectiveness of the Company's internal control over financial reporting, there has been (i) no material weakness in the Company's internal control over financial reporting (whether or not remediated) and (ii) no change in the Company's internal control over financial reporting that has materially affected, or is reasonably likely to materially affect, the Company's internal control over financial reporting.

        (y)   The Company (i) is an "air carrier" within the meaning of 49 U.S.C. Section 40102(a); (ii) holds an air carrier operating certificate issued by the Secretary of Transportation pursuant to Chapter 447 of Title 49 of the United States Code for aircraft capable of carrying 10 or more individuals or 6,000 pounds or more of cargo; and (iii) is a "citizen of the United States" as defined in 49 U.S.C. Section 401102.

        SECTION 2. Agreements To Sell and Purchase . The Company hereby agrees to sell to the several Underwriters, and each Underwriter, upon the basis of the representations and warranties herein contained, but subject to the conditions hereinafter stated, agrees, severally and not jointly, to purchase from the Company the respective principal amounts of Firm Securities set forth in Schedule II hereto opposite its name at the purchase price set forth in Schedule I hereto.

        On the basis of the representations and warranties contained in this Agreement, and subject to its terms and conditions, the Company agrees to issue and sell to the Underwriters the Additional Securities, and the Underwriters shall have the right to purchase, severally and not jointly, up to $12,000,000 principal amount of Additional Securities at the Purchase Price plus accrued interest, if any, to the date of payment and delivery. You may exercise this right on behalf of the Underwriters in whole or from time to time in part by giving written notice of each election to exercise the option not later than 30 days after the date of this Agreement. Any exercise notice shall specify the principal

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amount of Additional Securities to be purchased by the Underwriters and the date on which such securities are to be purchased. Each purchase date must be at least one business day after the written notice is given and may not be earlier than the Closing Date for the Firm Securities nor later than ten business days after the date of such notice. Additional Securities may be purchased as provided in Section 4 hereof solely for the purpose of covering over allotments made in connection with the offering of the Firm Securities. On each day, if any, that Additional Securities are to be purchased (an " Option Closing Date "), each Underwriter agrees, severally and not jointly, to purchase the principal amount of Additional Securities (subject to such adjustments to eliminate fractional securities as you may determine) that bears the same proportion to the total number of Additional Securities to be purchased on such Option Closing Date as the principal amount of Firm Securities set forth in Schedule II hereto opposite the name of such Underwriter bears to the total principal amount of Firm Securities.

        The Company hereby agrees that, without the prior written consent of Morgan Stanley & Co. Incorporated and Citigroup Global Markets Inc. on behalf of the Underwriters, it will not, during the period ending 90 days after the date of the Prospectus, (i) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock or any securities convertible into or exercisable or exchangeable for Common Stock or (ii) enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the Common Stock, whether any such transaction described in clause (i) or (ii) above is to be settled by delivery of Common Stock or such other securities, in cash or otherwise.

        The foregoing sentence shall not apply to (i) the Securities to be sold hereunder or the Underlying Securities, (ii) the issuance by the Company of shares of Common Stock upon the exercise of an option or warrant or the conversion of a security outstanding on the date hereof and as described in the Prospectus or (iii) the issuance by the Company of any shares of Common Stock, options, or other securities to or for the benefit of employees of the Company on or after the date hereof pursuant to the Company's employee stock ownership plan or equity incentive plans as described in the Prospectus and the issuance by the Company of shares of Common Stock upon the exercise of any such options.

        SECTION 3. Terms of Public Offering . You have advised the Company that the Underwriters propose to make a public offering of their respective portions of the Securities as soon after the Registration Statement and this Agreement have become effective as in your judgment is advisable.

        SECTION 4. Payment and Delivery . Payment for the Firm Securities shall be made to the Company in Federal or other funds immediately available in New York City against delivery of such Firm Securities for the respective accounts of the several Underwriters at 10:30 a.m., New York City time, on December 7, 2005, or at such other time on the same or such other date, not later than December 14, 2005, as shall be designated in writing by you. The time and date of such payment are hereinafter referred to as the " Closing Date. "

        Payment for any Additional Securities shall be made to the Company in Federal or other funds immediately available in New York City against delivery of such Additional Securities for the respective accounts of the several Underwriters at 10:30 a.m., New York City time, on the date specified in the corresponding notice described in Section 3 or at such other time on the same or on such other date, in any event not later than January 10, 2006, as shall be designated in writing by you.

        The Firm Securities and Additional Securities shall be in definitive form or global form, as specified by you, and in such denominations as you shall request in writing not later than one full business day prior to the Closing Date or the applicable Option Closing Date, as the case may be. The Firm Securities and Additional Securities shall be delivered to you on the Closing Date or an Option Closing Date, as the case may be, for the respective accounts of the several Underwriters, with any

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transfer taxes payable in connection with the transfer of the Securities to the Underwriters duly paid, against payment of the Purchase Price therefor plus accrued interest, if any, to the date of payment and delivery.

        SECTION 5. Conditions to the Underwriters' Obligations . The obligations of the Company to sell the Securities to the Underwriters and the several obligations of the Underwriters to purchase and pay for the Securities on the Closing Date are subject to the following conditions:

        (a)   Subsequent to the execution and delivery of this Agreement and prior to the Closing Date:

        (i)    there shall not have occurred any downgrading, nor shall any notice have been given of any intended or potential downgrading or of any review for a possible change that does not indicate the direction of the possible change, in the rating accorded any of the Company's securities by any "nationally recognized statistical rating organization," as such term is defined for purposes of Rule 436(g)(2) under the Securities Act; and

        (ii)   there shall not have occurred any change, or any development involving a prospective change, in the condition, financial or otherwise, or in the earnings, business or operations of the Company, from that set forth in the Time of Sale Prospectus (exclusive of any amendments or supplements thereto subsequent to the date of this Agreement) that, in your judgment, is material and adverse and that makes it, in your judgment, impracticable to market the Securities on the terms and in the manner contemplated in the Time of Sale Prospectus.

        (b)   The Underwriters shall have received on the Closing Date a certificate, dated the Closing Date and signed by an executive officer of the Company, to the effect set forth in Section 5(a)(i) above and to the effect that the representations and warranties of the Company contained in this Agreement are true and correct as of the Closing Date and that the Company has complied in all material respects with all of the agreements and satisfied in all material respects all of the conditions on its part to be performed or satisfied hereunder on or before the Closing Date. The officer signing and delivering such certificate may rely upon the best of his or her knowledge as to proceedings threatened.

        (c)   The Underwriters shall have received on the Closing Date an opinion of Faegre & Benson LLP, outside counsel for the Company, dated the Closing Date, to the effect that:

        (i)    the Company has been duly incorporated, is validly existing as a corporation in good standing under the laws of the jurisdiction of its incorporation, has the corporate power and authority to own its property and to conduct its business as described in the Time of Sale Prospectus and (based solely on an examination of certificates of government officials and agencies) is duly qualified to transact business and is in good standing in each jurisdiction set forth in a schedule to such opinion, except where the failure to be so qualified or be in good standing would not have a material adverse effect on the Company;

        (ii)   the authorized capital stock of the Company conforms as to legal matters in all material respects to the description thereof contained in the Time of Sale Prospectus;

        (iii)  the shares of capital stock of the Company outstanding prior to the issuance of the Securities have been duly authorized and are validly issued and, to the knowledge of such counsel, fully paid and non-assessable;

        (iv)  the Securities have been duly authorized and, when executed and authenticated in accordance with the provisions of the Indenture and delivered to and paid for by the Underwriters in accordance with the terms of this Agreement, will be valid and binding obligations of the Company, enforceable in accordance with their terms, subject to the effects

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of applicable bankruptcy, insolvency and similar laws affecting creditors' rights generally and equitable principles of general applicability, and will be entitled to the benefits of the Indenture;

        (v)   the Underlying Securities issuable upon conversion of the Securities have been duly authorized and reserved and, when issued upon conversion of the Securities in accordance with the terms of the Securities, will be validly issued, fully paid and non-assessable, and the issuance of the Underlying Securities will not be subject to any preemptive or similar rights under (A) the laws of the State of Colorado; (B) the articles of incorporation or by-laws of the Company or (C) to the knowledge of such counsel, any agreement or instrument to which the Company is a party;

        (vi)  the Indenture has been duly authorized, executed and delivered by, and is a valid and binding agreement of, the Company, enforceable in accordance with its terms, subject to the effects of applicable bankruptcy, insolvency and similar laws affecting creditors' rights generally and equitable principles of general applicability; and the Indenture has been duly qualified under the Trust Indenture Act;

        (vii) this Agreement has been duly authorized, executed and delivered by the Company;

        (viii)   except for such conflicts or violations, when considered alone or taken together with all other conflicts or violations, would not have a material adverse effect on the Company, the execution and delivery by the Company of, and the performance by the Company of its obligations under, this Agre