American Airlines seats can generally be selected during booking or after booking your flight. However, you'll need to avoid basic economy fares to get free seat selection. And you'll only get free preferred or extra-legroom seat selection if you have elite status or use miles to pay the fee.

On American Airlines, Preferred Seats are not "free" for standard Main Cabin passengers, but they are available at no extra cost to several groups of travelers. Preferred Seats are standard economy seats located in more desirable parts of the plane, such as closer to the front or in window/通用 rows, though they do not offer extra legroom like "Main Cabin Extra" does. These seats are free for AAdvantage status members (Gold, Platinum, Platinum Pro, and Executive Platinum) and their companions, as well as for those traveling on "Full Fare" (Y-class) tickets. Additionally, certain partners like Alaska Airlines status members or those with one-world Ruby, Sapphire, or Emerald status can select these seats for free at the time of booking. For everyone else, the cost usually ranges from $10 to $70 depending on the route. If seats remain unassigned as the flight approaches departure, they may be assigned for free by the gate agent, but this is not guaranteed.