Exhibit 5.1

300 North LaSalle Chicago, Illinois 60654   (312) 862-2000   www.kirkland.com Facsimile: (312) 862-2200

February 26, 2015

The Boeing Company

100 North Riverside

Chicago, Illinois 60606-1596

Re: Registration Statement on Form S-3

Ladies and Gentlemen:

We are issuing this opinion letter in our capacity as legal counsel to The Boeing Company, a Delaware corporation (the “Company”), in connection with the preparation of the Registration Statement on Form S-3 (such Registration Statement, as amended or supplemented, is hereinafter referred to as the “Registration Statement”) filed by the Company with the Securities and Exchange Commission (the “Commission”) on or about February 26, 2015, under the Securities Act of 1933, as amended (the “Securities Act”). The Registration Statement relates to the issuance and sale from time to time, pursuant to Rule 415 of the General Rules and Regulations promulgated under the Securities Act, of an unspecified amount of the following securities: (i) one or more series of unsecured senior debt securities of the Company, which may be convertible into Common Stock (as defined below) (the “Senior Debt Securities”); (ii) one or more unsecured series of subordinated debt securities of the Company, which may be convertible into Common Stock (the “Subordinated Debt Securities” and, together with the Senior Debt Securities, the “Debt Securities”); and (iii) shares of common stock, par value $5.00 per share, of the Company (the “Common Stock” and, together with the Debt Securities, the “Securities”). You have advised us that (i) the Senior Debt Securities will be issued under the indenture filed as an exhibit to the Registration Statement (as amended or supplemented from time to time, the “Senior Debt Indenture”) dated 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 (the “Senior Debt Trustee”); and (ii) the Subordinated Debt Securities will be issued under the form of indenture filed as an exhibit to the Registration Statement (as amended or supplemented from time to time, the “Subordinated Debt Indenture” and, together with the Senior Debt Indenture, the “Indentures”), to be entered into between the Company and a trustee (the “Subordinated Debt Trustee”, and, together with the Senior Debt Trustee, the “Trustees”).

In connection with the registration of the Securities, we have examined originals, or copies certified or otherwise identified to our satisfaction, of such documents, corporate records and other instruments as we have deemed necessary for the purposes of this opinion, including: (i) the organizational documents of the Company; (ii) minutes and records of the corporate proceedings of the Company, including the Board of Directors of the Company; and (iii) the Registration Statement and the exhibits thereto.

For purposes of this opinion, we have assumed the authenticity of all documents submitted to us as originals, the conformity to the originals of all documents submitted to us as copies and the authenticity of the originals of all documents submitted to us as copies. We have also assumed the legal capacity of all natural persons, the genuineness of the signatures of persons signing all documents in connection with which this opinion is rendered, the authority of such persons signing on behalf of the parties thereto other than the Company, and the due authorization, execution and delivery of all documents by the parties thereto other than the Company. As to any facts material to the opinions expressed herein that we have not independently established or verified, we have relied upon statements and representations of officers and other representatives of the Company.

We have also assumed that:

(i) the Registration Statement and any amendments thereto (including post-effective amendments) will be effective and will comply with all applicable laws at the time the Securities are offered or issued as contemplated by the Registration Statement;

(ii) a prospectus supplement or term sheet (“Prospectus Supplement”) will have been prepared and filed with the Commission describing the Securities offered thereby and will comply with all applicable laws;

(iii) all Securities will be issued and sold in compliance with applicable federal and state securities laws and in the manner stated in the Registration Statement and the appropriate Prospectus Supplement;

(iv) the Securities will be issued and sold in the form and containing the terms set forth in the Registration Statement, the appropriate Prospectus Supplement and the Indenture;

(v) the Securities offered, as well as the terms of the Indentures, as they are or will be executed and delivered, do not violate any law applicable to the Company or result in a default under or breach of any agreement or instrument binding upon the Company;

(vi) the Company will have obtained any legally required consents, approvals, authorizations and other orders of the Commission and any other regulatory authorities necessary to issue and sell the Securities being offered and to execute and deliver the Indentures;

(vii) the Securities offered as well as the terms of the Indentures, as they will be executed and delivered, comply with all requirements and restrictions, if any, applicable to the Company, whether imposed by any court or governmental or regulatory body having jurisdiction over the Company;

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(viii) the Indentures and the Trustees are or will have been qualified under the Trust Indenture Act of 1939, as amended; and

(ix) a definitive purchase, underwriting or similar agreement (each, a “Purchase Agreement”) with respect to any Securities offered or issued will have been duly authorized and validly executed and delivered by the Company and the other parties thereto.

Based upon and subject to the foregoing qualifications, assumptions and limitations and the further limitations set forth below, we are of the opinion that:

1. When, as and if (a) the terms of any particular series of Senior Debt Securities have been duly authorized pursuant to resolutions of the Board of Directors of the Company and duly established in accordance with the Senior Debt Indenture, and applicable law, (b) the appropriate corporate or organizational action has been taken to authorize the form, terms, execution and delivery of such Senior Debt Securities (and any required amendment or supplement to the Senior Debt Indenture), and (c) the applicable Senior Debt Securities have been duly executed, attested, issued and delivered by duly authorized officers against payment in accordance with such authorization, the Senior Debt Indenture, the applicable Purchase Agreement and applicable law and authenticated by the Senior Debt Trustee, such Senior Debt Securities will constitute valid and binding obligations of the Company enforceable against the Company in accordance with their terms.

2. When, as and if (a) the terms of any particular series of Subordinated Debt Securities have been duly authorized pursuant to resolutions of the Board of Directors of the Company and duly established in accordance with the Subordinated Debt Indenture and applicable law, (b) the appropriate corporate or organizational action has been taken to authorize the form, terms, execution and delivery of such Subordinated Debt Securities (and any required amendment or supplement to the Subordinated Debt Indenture), and (c) the applicable Subordinated Debt Securities have been duly executed, attested, issued and delivered by duly authorized officers against payment in accordance with such authorization, the Subordinated Debt Indenture, the applicable Purchase Agreement and applicable law and authenticated by the Subordinated Debt Trustee, such Subordinated Debt Securities will constitute valid and binding obligations of the Company enforceable against the Company in accordance with their terms.

3. When issued pursuant to resolutions of the Board of Directors of the Company and in accordance with the conversion provisions of Debt Securities and in a manner so as not to violate any applicable law or agreement or instrument then binding on the Company and delivered against payment therefor in accordance with Debt Securities (which shall be in an amount at least equal to the par value of the shares being issued and sold) that have been duly authorized executed and delivered, shares of Common Stock so issued will be validly issued, fully paid and non-assessable.

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Our opinions expressed above are subject to the qualifications that we express no opinion as to the applicability of, compliance with, or effect of (i) any bankruptcy, insolvency, reorganization, fraudulent transfer, fraudulent conveyance, moratorium or other similar law affecting the enforcement of creditors’ rights generally, (ii) general principles of equity (regardless of whether enforcement is considered in a proceeding in equity or at law), (iii) public policy considerations which may limit the rights of parties to obtain certain remedies and (iv) any laws except the laws of the State of New York and the General Corporation Law of the State of Delaware, including the applicable provisions of the Delaware constitution and reported judicial decisions interpreting these laws.

We express no opinion with respect to the enforceability of: (i) consents to, or restrictions upon, judicial relief or jurisdiction or venue; (ii) waivers of rights or defenses with respect to stay, extension or usury laws; (iii) advance waivers of claims, defenses, rights granted by law, or notice, opportunity for hearing, evidentiary requirements, statutes of limitation, trial by jury or at law, or other procedural rights; (iv) waivers of broadly or vaguely stated rights; (v) provisions for exclusivity, election or cumulation of rights or remedies; (vi) provisions authorizing or validating conclusive or discretionary determinations; (vii) grants of setoff rights; (viii) provisions for the payment of attorneys’ fees where such payment is contrary to law or public policy; (ix) proxies, powers and trusts; (x) restrictions upon non-written modifications and waivers; (xi) provisions prohibiting, restricting, or requiring consent to assignment or transfer of any right or property; (xii) any provision to the extent it requires any party to indemnify any other person against loss in obtaining the currency due following a court judgment in another currency; and (xiii) provisions for liquidated damages, default interest, late charges, monetary penalties, make-whole premiums or other economic remedies to the extent such provisions are deemed to constitute a penalty. In addition, we express no opinion with respect to (i) whether acceleration of the Debt Securities may affect the collectability of that portion of the stated principal amount thereof that might be determined to constitute unearned interest thereon, (ii) compliance with laws relating to permissible rates of interest or (iii) the creation, validity, perfection or priority of any security interest or lien.

To the extent that the obligations of the Company under the Indentures may be dependent on such matters, we assume for purposes of this opinion that the applicable Trustee is duly organized, validly existing and in good standing under the laws of its jurisdiction of organization; that the applicable Trustee is duly qualified to engage in the activities contemplated by the Indentures; that the applicable Indenture has been duly authorized, executed and delivered by the applicable Trustee and constitutes the legally valid and binding obligation of such Trustee, enforceable against such Trustee in accordance with its terms; that applicable Trustee is in compliance, generally and with respect to acting as an agent under the applicable Indenture with all applicable laws and regulations; and that the applicable Trustee has the requisite organizational and legal power and authority to perform its obligations under the applicable Indenture.

We hereby consent to the filing of this opinion with the Commission as Exhibit 5.1 to the Registration Statement. We also consent to the reference to our firm under the heading “Legal Matters” in the Registration Statement. In giving this consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

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We do not find it necessary for the purposes of this opinion, and accordingly we do not purport to cover herein, the application of the securities or “blue sky” laws of the various states to the sale of the Securities.

This opinion is limited to the specific issues addressed herein, and no opinion may be inferred or implied beyond that expressly stated herein. The Securities may be issued from time to time on a delayed or continuous basis, and this opinion is limited to the laws, including the rules and regulations, as in effect on the date hereof, which laws are subject to change with possible retroactive effect. We assume no obligation to revise or supplement this opinion should the present internal law of the State of New York or the General Corporation Law of the State of Delaware be changed by legislative action, judicial decision or otherwise.

This opinion is furnished to you in connection with the filing of the Registration Statement, and is not to be used, circulated, quoted or otherwise relied upon for any other purpose.

Yours very truly,

/s/ KIRKLAND & ELLIS LLP

KIRKLAND & ELLIS LLP

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