X0306 4 2021-09-24 0001701732 Altair Engineering Inc. ALTR 0001720807 Christ George J C/O ALTAIR ENGINEERING INC. 1820 E. BIG BEAVER RD. TROY MI 48083 1 Class A Common Stock 2021-09-24 4 C 0 374950 0 A 374950 I By Christ Revocable Trust dated May 8, 2015 Class A Common Stock 2021-09-24 5 G 0 E 187475 0 D 187475 I By Christ Revocable Trust dated May 8, 2015 Class A Common Stock 2021-09-24 5 G 0 E 187475 0 D 0 I By Christ Revocable Trust dated May 8, 2015 Class A Common Stock 187475 I By The Dana Christ Irrevocable Trust Dated May 8, 2015 Class A Common Stock 187475 I By The Lauren Christ Irrevocable Trust Dated May 8, 2015 Class B Common Stock 0 2021-09-24 4 C 0 374950 0 D Class A Common Stock 374950 5881778 I By Christ Revocable Trust dated May 8, 2015 Class B Common Stock 0 Class A Common Stock 4944004 4944004 I By GC Investments LLC Reporting person serves as Trustee. Reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of all of the reported shares for purposes of Section 16 or for any other purpose. On September 24, 2021, the reporting person transferred 187,475 shares of Class A common stock to a family trust of which the reporting person serves as co-Trustee. A member of the reporting person's immediate family is the sole beneficiary of the trust." Reporting person serves as co-Trustee. Reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of all of the reported shares for purposes of Section 16 or for any other purpose. Each share of Class B common stock is immediately convertible, at the option of the shareholder, into one share of Class A common stock and shall automatically convert into Class A common stock upon the occurrence of certain events. Please see Altair Engineering Inc. Registration Statement filed with the Securities and Exchange Commission on Form S-1 (File No. 333-225412) for a description of the conversion rights. Reporting person serves as Manager. Reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of all of the reported shares for purposes of Section 16 or for any other purpose. /s/ Raoul Maitra, attorney-in-fact for George J. Christ 2021-09-27