X0609 4 2026-05-11 0001018963 ATI INC ATI 0001773072 Fields Kimberly A false C/O ATI INC. 2021 MCKINNEY AVE., SUITE 1100 DALLAS TX 75201 true true false false President, CEO and Director true Common Stock, par value $0.10 per share 2026-05-11 4 S false 1300 154.02 D 316463 D Common Stock, par value $0.10 per share 2026-05-11 4 S false 5568 156.29 D 310895 D Common Stock, par value $0.10 per share 2026-05-11 4 S false 3350 157.51 D 307545 D Common Stock, par value $0.10 per share 2026-05-11 4 S false 6420 158.38 D 301125 D Common Stock, par value $0.10 per share 2026-05-11 4 S false 2600 159.38 D 298525 D Common Stock, par value $0.10 per share 2026-05-11 4 S false 11982 160.60 D 286543 D Common Stock, par value $0.10 per share 2026-05-11 4 S false 8780 161.12 D 277763 D Shares sold pursuant to a 10b5-1 Trading Plan dated February 5, 2026, entered into for personal tax and estate planning purposes. The price reported is a weighted average price. The shares were sold in multiple transactions at prices ranging from $153.82 to $154.65. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the U.S. Securities and Exchange Commission (the "SEC"), upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. The shares were sold in multiple transactions at prices ranging from $155.78 to $156.76. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. The shares were sold in multiple transactions at prices ranging from $156.91 to $157.90. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $157.91 to $158.88. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $158.94 to $159.84. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $159.99 to 160.98. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $160.99 to 161.38. The reporting person undertakes to provide to the Issuer, its security holders and the Staff of the SEC, upon request, full information regarding the number of shares sold at each specific price within the range reported. /s/ Amanda J. Skov, Attorney-in-Fact for Kimberly A. Fields 2026-05-12