SCHEDULE 13D/A 0000950170-25-067179 0001801142 XXXXXXXX LIVE 2 Common Stock, par value $0.0001 per share 12/16/2025 false 0001994624 80603V203 ScanTech AI Systems Inc.

1735 Enterprise Drive Buford GA 30518

Stephen C. Smith (212) 616-7700 360 Madison Avenue 22nd Floor New York NY 10017 Louis Rambo (202) 416-6800 Proskauer Rose LLP 1001 Pennsylvania Ave. NW, Suite 600 Washington DC 20004 0001801142 N Seaport Global Asset Management LLC AF N NY 0 804867 0 804867 804867 N 21.3 IA HC Y Seaport Group SIBS LLC OO N DE 0 804867 0 804867 804867 N 21.3 CO 0001393195 N Stephen C. Smith AF N X1 0 804867 0 804867 804867 N 21.3 IN HC Common Stock, par value $0.0001 per share ScanTech AI Systems Inc. 1735 Enterprise Drive Buford GA 30518 Items 5(a)-(c) of the Schedule 13D are amended and supplemented as follows: The information set forth in rows 11 and 13 of the cover pages to this Schedule 13D is incorporated herein by reference. The percentages set forth in row 13 are based on approximately 3,780,656 shares of Common Stock outstanding, based on 75,613,124 shares of Common Stock outstanding as of December 11, 2025, as reported by the Issuer in its Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on December 15, 2025, and giving effect to the Issuer's one-for-twenty reverse stock split effected on December 16, 2025. The information set forth in rows 7 through 10 of the cover pages to this Schedule 13D is incorporated herein by reference. Schedule A to this Amendment No. 2 is incorporated by reference into this Item 5(c). Other than with respect to the transactions set forth in the disclosure incorporated by reference to this Item 5(c), none of the Reporting Persons has effected any transaction in the Issuer's securities since the filing of Amendment No. 1 to the Schedule 13D on October 15, 2025. Seaport Global Asset Management LLC /s/ Stephen C. Smith 12/18/2025 Seaport Group SIBS LLC /s/ Stephen C. Smith 12/18/2025 Stephen C. Smith /s/ Stephen C. Smith 12/18/2025