Upvote:10
According to https://www.plussizetraveltoo.com/2022/02/north-american-customer-of-size-policies/ the seats on American Airlines planes are 17 inches wide in the Main Cabin. Main Cabin Extra is no bigger, however Premium Economy and Business range from 18.5 inches to 21.9 inches. The seatbelt on American Airlines planes is 45 to 47 inches wide.
American Airlines Extra Space During Travel policy says:
“If a customer needs extra space outside a single seat to travel safely, another seat is required. We encourage customers to address all seating needs when booking.
Source: https://www.aa.com/i18n/travel-info/special-assistance/special-assistance.jsp#extraspace