How do I change my seat assignment on my American Airlines flight after check-in?

If you need to change your seat assignment on an American Airlines flight after checking in, you can do so easily on the airline's website or mobile app. Here are the steps:

1. Go to the American Airlines website or mobile app and log in to your account.
2. Click on the 'Manage Reservations' or 'My Trips' section, and find your flight reservation.
3. Select the flight you want to change your seat assignment for.
4. Click on the 'Change Seats' button.
5. Choose your new seat assignment from the available options, and confirm the changes.

If there are no available seats for you to select, you may need to contact American Airlines customer service for assistance. Additionally, please note that changing your seat assignment may result in additional fees.

It is recommended to change your seat assignment as soon as possible to ensure you get the seat you want.