PURCHASE AGREEMENT

Exhibit 1.1

THE BOEING COMPANY

Unsecured Debt Securities

PURCHASE AGREEMENT

July 23, 2009

The Boeing Company

100 North Riverside

Chicago, Illinois 60606

Ladies and Gentlemen:

Referring to the Unsecured Debt Securities of The Boeing Company (the “Company”) covered by the registration statement on Form S-3 (Registration No. 333-157790) (such registration statement, including (i) the prospectus included therein (the “Base Prospectus”), and (ii) all documents filed as part thereof or incorporated by reference therein including the information, if any, deemed pursuant to Rule 430A, 430B or 430C under the Securities Act of 1933, as amended (the “Securities Act”) to be part of the registration statement at the time of its effectiveness, and at each deemed effective date with respect to the Purchasers (as defined below) pursuant to Rule 430B(f)(2) of the Securities Act, are hereinafter collectively called the “Registration Statement”). The Base Prospectus (i) as supplemented by the prospectus supplement dated July 23, 2009 specifically relating to the Purchased Notes (as defined below) in the form first filed under Rule 424(b) under the Securities Act (or in the form first made available to the Purchasers (as defined below) by the Company to meet the requests of purchasers pursuant to Rule 173 under the Securities Act) and (ii) all documents filed as part thereof or incorporated or deemed to be incorporated by reference therein are hereinafter collectively called the “Prospectus,” and the preliminary form of the Prospectus is hereinafter called the “Preliminary 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 each free writing prospectus, if any, identified in Schedule B hereto. “Time of Sale” means 4:15 pm (Eastern time) on the date of this Agreement. Any reference to “amend”, “amendment” or “supplement” with respect to the Registration Statement, any Preliminary Prospectus or the Prospectus shall be deemed to refer to and include any documents filed after such date under the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission thereunder (collectively, the “Exchange Act”) that are deemed to be incorporated by reference therein.

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On the basis of the representations, warranties and agreements contained in this Agreement, but subject to the terms and conditions herein set forth, the purchaser or purchasers named in Schedule A hereto (the “Purchasers”) agree to purchase, severally, and the Company agrees to sell to the Purchasers, severally, the respective principal amounts of the Company’s 3.500% Senior Notes due 2015 (the “2015 Notes”), 4.875% Senior Notes due 2020 (the “2020 Notes”) and 5.875% Senior Notes due 2040 (the “2040 Notes” and, together with the 2015 Notes and the 2020 Notes, the “Purchased Notes”) set forth opposite the name of each Purchaser on Schedule A hereto. The Purchased Notes will have the terms as set forth in the Pricing Term Sheet on Schedule B.

The price at which the Purchased Notes shall be purchased from the Company by the Purchasers shall be 98.807% of the principal amount of the 2015 Notes, 98.508% of the principal amount of the 2020 Notes and 96.805% of the principal amount of the 2040 Notes, plus, in each case, accrued interest, if any, from July 28, 2009, to the date of delivery. The initial public offering price shall be 99.157% of the principal amount of the 2015 Notes, 98.958% of the principal amount of the 2020 Notes and 97.680% of the principal amount of the 2040 Notes, plus, in each case, accrued interest, if any, from July 28, 2009 to the date of delivery. The Purchased Notes will be offered by the Purchasers as set forth in the Prospectus Supplement relating to such Purchased Notes.

The Company understands that the Purchasers intend to make a public offering of the Purchased Notes as soon after the effectiveness of this Agreement as in the judgment of the Purchasers is advisable, and initially to offer the Purchased Notes on the terms set forth in the Time of Sale Prospectus. The Company acknowledges and agrees that the Purchasers may offer and sell Purchased Notes to or through any affiliate of a Purchaser and that any such affiliate may offer and sell Purchased Notes purchased by it to or through any Purchaser.

If we are acting as Representative(s) for the several Purchasers named in Schedule A hereto, we represent that we are authorized to act for such several Purchasers in connection with the transactions contemplated in this Agreement, and that, if there are more than one of us, any action under this Agreement taken by any of us will be binding upon all the Purchasers.

All of the provisions contained in the document entitled “The Boeing Company Standard Purchase Provisions”, a copy of which is attached hereto, are hereby incorporated by reference in their entirety and shall be deemed to be a part of this Agreement to the same extent as if such provisions had been set forth in full herein, except that references in Section 10 of “The Boeing Company Standard Purchase Provisions” with respect to this Agreement only, are references to the 2015 Notes, the 2020 Notes, and 2040 Notes separately and Section 10 shall apply to each such series separately and not to all such series together.

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a “Relevant Member State”), each Purchaser hereby represents that it has not made and will not make an offer of the Notes to the public in that Relevant Member State, except that it may make an offer of the Notes to the public in that Relevant

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Member State at any time under the following exemptions under the Prospectus Directive (as defined below), if they have been implemented in that Relevant Member State: (a) to legal entities which are authorized or regulated to operate in the financial markets or, if not so authorized or regulated, whose corporate purpose is solely to invest in securities; (b) to any legal entity which has two or more of (1) an average of at least 250 employees during the last financial year; (2) a total balance sheet of more than €43,000,000 and (3) an annual net turnover of more than €50,000,000, as shown in its last annual or consolidated accounts; (c) to fewer than 100 natural or legal persons (other than qualified investors as defined in the Prospectus Directive); or (d) in any other circumstances falling within Article 3(2) of the Prospectus Directive, provided that no such offer of Notes shall result in a requirement for the publication by the Company or any underwriter of a prospectus pursuant to Article 3 of the Prospectus Directive. For purposes of this section, the expression an “offer of the Notes to the public” in relation to any Notes in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the Notes to be offered so as to enable an investor to decide to purchase or subscribe to purchase the Notes, as the same may be varied in the Relevant Member State by any measure implementing the Prospectus Directive in that Relevant Member State, and the expression Prospectus Directive means Directive 2003/71/EC and includes any relevant implementing measure in each Relevant Member State.

Each Purchaser hereby represents that, in connection with the distribution of the Notes, it has only communicated or caused to be communicated and will only communicate or cause to be communicated any invitation or inducement to engage in investment activity (within the meaning of Section 21 of the Financial Services and Markets Act 2000 (“FSMA”) of the United Kingdom) received by it in connection with the issue or sale of the Notes or any investments representing the Notes in circumstances in which Section 21(1) of the FSMA does not apply to the Company and that it has complied and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the Notes in, from or otherwise involving the United Kingdom.

Each Purchaser that is not a U.S. registered broker-dealer, represents that if it sells Notes in the United States it will do so through one or more U.S. registered broker-dealers as permitted by the Financial Industry Regulatory Authority regulations.

Each Purchaser hereby agrees that it will not offer, sell or deliver any of the Notes in any jurisdiction outside the United States except under circumstances that will result in compliance with the applicable laws thereof, and that it will take at its own expense whatever action is required to permit its resale of the Notes in such jurisdictions. Each Purchaser understands that no action has been taken to permit a public offering in any jurisdiction outside the United States where action would be required for such purpose. Each Purchaser agrees not to cause any advertisement of the Notes to be published in any newspaper or periodical or posted in any public place and not to issue any circular relating to the Notes, except in any such case with the prior express written consent of the Company and of the Representatives and then only at its own risk and expense.

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The “Closing Date” shall be:    July 28, 2009

Notices to the Purchasers shall be sent to the following address(es) or telecopier number(s):

Banc of America Securities LLC

One Bryant Park

NY1-100-18-03

New York, New York 10036

Attention: High Grade Transaction Management/Legal

Facsimile: 646-855-5958

Deutsche Bank Securities Inc.

60 Wall Street

New York, New York 10005

Attention: Debt Capital Markets - Syndicate Desk

Facsimile: 212-797-2202

Morgan Stanley & Co. Incorporated

1585 Broadway, 29th Floor

New York, New York 10036

Attention: Investment Banking Division

Facsimile: 212-507-8999

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If the foregoing is in accordance with your understanding of our agreement, kindly sign and return to us the enclosed duplicate hereof, whereupon it will become a binding agreement between the Company and the several Purchasers in accordance with its terms.

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SCHEDULE A

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SCHEDULE B

Filed Pursuant to Rule 433 under the Securities Act of 1933

Registration Statement No. 333-157790

Issuer Free Writing Prospectus, dated July 23, 2009

$1,950,000,000

Senior Notes Offering

Summary of Final Terms

Dated July 23, 2009

Notes:

The issuer has filed a registration statement (including a prospectus) with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC Web site at www.sec.gov. Alternatively, the issuer, any underwriter or any dealer participating in the offering will arrange to send you the prospectus if you request it by calling Banc of America Securities LLC toll-free at 1-800-294-1322, Deutsche Bank Securities Inc. toll-free at 1-800-503-4611 or Morgan Stanley & Co. Incorporated toll-free at 1-866-718-1649.

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THE BOEING COMPANY

STANDARD PURCHASE PROVISIONS

From time to time, The Boeing Company, a Delaware corporation (“Company”), may enter into purchase agreements that provide for the sale of designated securities to the purchaser or purchasers named therein. The standard provisions set forth herein may be incorporated by reference in any such purchase agreement (“Purchase Agreement”). The Purchase Agreement, including the provisions incorporated therein by reference, is herein sometimes referred to as “this Agreement.” Unless otherwise defined herein, terms defined in the Purchase Agreement are used herein as therein defined.

1. Introductory . The Company proposes to issue and sell from time to time its Unsecured Debt Securities (“Notes”) registered under the registration statement referred to in Section 2(a). The Notes will be issued under an Indenture, dated as of February 1, 2003, between the Company and The Bank of New York Mellon Trust Company, N.A., as successor to JPMorgan Chase Bank, as Trustee, as may be supplemented from time to time, (the “Indenture”). The Notes will be sold to the Purchasers (as defined below) for resale in accordance with the terms of the offering determined at the time of the sale. The Notes involved in any such offering are hereinafter referred to as the “Purchased Notes,” and the firm or firms, as the case may be, which agree to purchase the same are hereinafter referred to as the “Purchasers” of such Purchased Notes. The terms “you” and “your” refer to those Purchasers who sign the Purchase Agreement either on behalf of themselves only or on behalf of themselves and as representatives of the several Purchasers named in Schedule A thereto, as the case may be.

2. Representations and Warranties of the Company . The Company represents and warrants to and agrees with each Purchaser that:

(a) A Registration Statement (as defined in the Purchase Agreement) covering an indeterminate amount of the securities of the Company (including the Purchased Notes), including a prospectus has been filed with the Securities and Exchange Commission (“Commission”) and has become effective under the Securities Act of 1933, as amended (the “Securities Act”); no stop order suspending the effectiveness of the Registration Statement is in effect, and no proceedings for such purpose are pending before or threatened by the Commission. The Company is a well known seasoned issuer (as defined in Rule 405 under the Securities Act) eligible to use the Registration Statement as an automatic shelf registration statement and the Company has not received notice that the Commission objects to the use of the Registration Statement as an automatic shelf registration statement. The terms Registration Statement, Time of Sale Prospectus and Prospectus shall have the meanings ascribed to them in the Purchase Agreement.

(b) The Company is not an “ineligible issuer” in connection with the offering 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 (the “Securities Act Rules and Regulations”). 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 on 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 B to the Purchase Agreement, 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.

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(c) The Registration Statement conforms in all respects to the requirements of the Securities Act and the Securities Act Rules and Regulations and does not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading, except that the foregoing does not apply to statements or omissions in such document based upon written information furnished to the Company by any Purchaser specifically for use therein. At the Time of Sale, the Time of Sale Prospectus did 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 foregoing does not apply to statements or omissions in such document based upon written information furnished to the Company by any Purchaser specifically for use therein. 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 foregoing does not apply to statements or omissions in such document based upon written information furnished to the Company by any Purchaser specifically for use therein. The documents incorporated by reference in the Registration Statement, the Time of Sale Prospectus or the Prospectus pursuant to Item 12 of Form S-3 of the Securities Act, at the time they were filed with the Commission, complied in all material respects with the requirements of the Securities Exchange Act of 1934, as amended, and the pertinent published rules and regulations thereunder (the “Exchange Act Rules and Regulations”). Any additional documents deemed to be incorporated by reference in the Time of Sale Prospectus or the Prospectus, will, when they are filed with the Commission, comply in all material respects with the requirements of the Exchange Act and the Exchange Act Rules and Regulations and will not contain an 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, in light of the circumstances under which they were made, not misleading.

(d) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Delaware, with power and corporate authority to own its properties and conduct its business as described in the Registration Statement, Time of Sale Prospectus and the Prospectus; and the Company is duly qualified to do business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification except where failure to so qualify would not individually or in the aggregate have a material adverse effect on the financial condition, business, properties or results of operations of the Company and its subsidiaries taken as a whole or on the Company’s ability to perform its obligations under the Offered Securities and the Indenture in any material respect (a “Material Adverse Effect”).

(e) Each “significant subsidiary” (as such term is defined in Rule 1-02 of Regulation S-X) of the Company (e