FORM 4 [ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES
                                                                                  
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                      
1. Name and Address of Reporting Person * Howley W Nicholas 2. Issuer Name and Ticker or Trading Symbol TransDigm Group INC [ TDG ] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable)__X__ Director                    _____ 10% Owner
__X__ Officer (give title below)    _____ Other (specify below)
Exec. Chairman of the Board
(Last)         (First)         (Middle)
1301 EAST NINTH STREET, SUITE 3000
3. Date of Earliest Transaction (MM/DD/YYYY)
4/15/2021
(Street)
CLEVELAND, OH 44114
(City)       (State)       (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)
 
6. Individual or Joint/Group Filing (Check Applicable Line) _X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. Code
(Instr. 8)
4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)
6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock  4/15/2021    M    11500  A $130.09  33047.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    1363  D $620.0622 (1) 31684.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    3151  D $621.0022 (2) 28533.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    3338  D $621.7507 (3) 25195.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    1419  D $622.7258 (4) 23776.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    721  D $623.7389 (5) 23055.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    1007  D $625.0862 (6) 22048.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    301  D $626.4413 (7) 21747.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 
Common Stock  4/15/2021    S    200  D $628.922 (8) 21547.513  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security 3. Trans. Date 3A. Deemed Execution Date, if any 4. Trans. Code
(Instr. 8)
5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
6. Date Exercisable and Expiration Date 7. Title and Amount of Securities Underlying Derivative Security
(Instr. 3 and 4)
8. Price of Derivative Security
(Instr. 5)
9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option  $130.09  4/15/2021    M        11500   9/30/2016  11/19/2022  Common Stock  11500  $0.00  207000  I  W. Nicholas Howley Family Trust u/a/d 4/23/99 

Explanation of Responses:
(1)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $619.36 - $620.31. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.
(2)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $620.39 - $621.37. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.
(3)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $621.39 - $622.37. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.
(4)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $622.40 - $623.32. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.
(5)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $623.42 - $624.29. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.
(6)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $624.78 - $625.70. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.
(7)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $625.83 - $626.62. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.
(8)  Price reported constitutes the average weighted price of shares sold. Shares were sold at varying prices in the range of $628.86 - $629.03. The reporting person hereby undertakes, upon request of the Commission, the issuer or a security holder of the issuer, to provide full information regarding the number of shares sold at each separate price.

Remarks:
All transactions reported hereunder were made pursuant to an established 10B5-1 plan.

Reporting Owners
Reporting Owner Name / Address
Relationships
Director 10% Owner Officer Other
Howley W Nicholas
1301 EAST NINTH STREET
SUITE 3000
CLEVELAND, OH 44114
X
Exec. Chairman of the Board

Signatures
Halle Martin as Attorney in fact for W Nicholas Howley. 4/15/2021
**Signature of Reporting Person Date