First Amendment to Agreement and Plan of Merger, dated as of October 10, 2018, by and among Esterline Technologies Corporation, TransDigm Group Incorporated and Thunderbird Merger Sub Inc

Exhibit 2.1

FIRST AMENDMENT TO

AGREEMENT AND PLAN OF MERGER

This FIRST AMENDMENT TO AGREEMENT AND PLAN OF MERGER (this “Amendment”), dated as of October 10, 2018, is by and among ESTERLINE TECHNOLOGIES CORPORATION, a Delaware corporation (the “Company”), TRANSDIGM GROUP INCORPORATED, a Delaware corporation (“Parent”), and THUNDERBIRD MERGER SUB INC., a Delaware corporation (“Merger Sub” and, together with the Company and Parent, the “Parties”). Capitalized terms used and not otherwise defined herein have the meanings ascribed to them in the Merger Agreement (defined below).

RECITALS

WHEREAS, the Parties entered into the Agreement and Plan of Merger, dated as of October 9, 2018 (the “Merger Agreement”);

WHEREAS, pursuant to Section 8.08 of the Merger Agreement, the Merger Agreement may be amended, modified and supplemented pursuant to an instrument in writing executed by the Parties; and

WHEREAS, the Parties desire to amend the Merger Agreement as set forth in this Amendment.

NOW, THEREFORE, in consideration of the foregoing Recitals and for other good and valuable consideration, the receipt and sufficiency of which are acknowledged, and intending to be legally bound by this Amendment, the Parties agree as follows:

“(c) Parent shall not, and shall cause its Subsidiaries not to, take any action, including acquiring any asset, property, business or Person (by way of merger, consolidation, share exchange, investment, other business combination, asset, stock or equity purchase, or otherwise), in each case, that could reasonably be expected to adversely affect obtaining or making any Consent or Filing contemplated by this Section 5.05 or the timely receipt thereof. In furtherance of and without limiting any of Parent’s covenants and agreements under this Section 5.05, Parent shall take all reasonable actions necessary, proper or advisable to avoid or eliminate each and every impediment that may be asserted by a Governmental Authority with respect to the Merger, including pursuant to any Antitrust Law, so as to enable the Closing to occur as soon as reasonably possible (and in each case, sufficiently before the End Date in order to allow Closing by the End Date), including (i) proposing, negotiating, committing to and effecting, by consent decree, hold separate orders, or otherwise, the sale, divestiture or disposition of such of its or the Company’s assets, properties or businesses or of the assets, properties or businesses to be acquired by it pursuant hereto, and the entrance into such other arrangements, including entering into customary ancillary agreements on commercially reasonable terms relating to any such sale, divestiture, licensing or disposition, in order to avoid the entry of, or to have vacated, lifted, reversed or overturned any decree, judgment, injunction or other

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order, whether temporary, preliminary or permanent, that would prevent the consummation of the transactions contemplated hereby as soon as practicable; (ii) agreeing to any limitation on the conduct of Parent or its Subsidiaries (including, after the Closing, the Surviving Corporation and the Company Subsidiaries); and (iii) agreeing to take any other action or make any other commitment as may be required by a Governmental Authority in order to effect each of the following: (A) obtaining the HSR Clearance and any other Consent of a Governmental Authority under any Antitrust Law that is required to consummate the Merger, in each case, as promptly as practicable and in any event before the End Date; (B) obtaining the French Foreign Investment Clearance; (C) avoiding the entry of, or having vacated, lifted, dissolved, reversed or overturned any Judgment, whether temporary, preliminary or permanent, that is in effect that prohibits, prevents or restricts consummation of, or impedes, interferes with or delays, the Closing on or before the End Date; (D) effecting the expiration or termination of any waiting period, which would otherwise have the effect of preventing, prohibiting or restricting consummation of the Closing or impeding, interfering with or delaying the Closing (such actions in clauses (i) through (iii) “Antitrust Actions”); provided, however, that (x) any such Antitrust Actions are conditioned upon the closing of the Merger and become effective only from and after the Effective Time and (y) notwithstanding any provision of this Agreement, Parent shall not be required to propose, negotiate, commit to, effect and agree to Antitrust Actions relating to the businesses, assets, properties, product lines, equity interests, relationships, ventures, contractual rights, or obligations of Parent and its Subsidiaries (including, prior to the Closing, the Company and its Subsidiaries, and following the Closing, the Surviving Corporation and its Subsidiaries) that, directly or indirectly, generated in the aggregate EBITDA in excess of $90,000,000 during the 12 calendar months ended September 30, 2018. The Parties agree that for the purposes of this Section 5.05(c), “EBITDA” means EBITDA as calculated by Parent in a manner consistent with the methodology utilized in the earnings releases Parent has publicly filed with the SEC. Without limiting the foregoing, in no event will the Company (and the Company will not permit any of its Subsidiaries to) propose, negotiate, effect or agree to any Antitrust Action without the prior written consent of Parent. For the avoidance of doubt, Antitrust Actions does not include a requirement for Parent to, in case any civil, criminal or administrative action, suit, litigation, arbitration, proceeding is instituted (or threatened to be instituted) challenging the consummation of the Merger or any other transaction contemplated by this Agreement as violative of any Antitrust Law, take any action to avoid the entry of, or to have vacated, lifted, reversed or overturned any order that would restrain, prevent or delay the Closing on or before the End Date, including no requirement to defend through litigation on the merits.”

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[SIGNATURE PAGES FOLLOW]

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IN WITNESS WHEREOF, the Parties have duly executed this Amendment, each as of the date first written above.

Signature Page to First Amendment to Agreement and Plan of Merger

Signature Page to First Amendment to Agreement and Plan of Merger