Upvote:0
You have probably chosen the ticket class that doesn't allow luggage ("Economy Basic" or similar), so you would have to buy it extra, either online or at the check-in desk.
If you know for sure you will have luggage, it is typically cheaper to buy the next higher ticket class ("Economy" or similar), which includes some luggage, plus seat selection, instead of paying through the nose for the luggage a check in)
Upvote:2
You can always add luggage at the airport after booking online. Make sure however your total number of bags are within the maximum limit.
You don’t want to show up at the airport with ten bags and you’re only allowed a total of five.
Bags − Travel information − American Airlines American Airlines
How does it work? You can choose to pay for up to 3 checked bags (per person) before arriving at the airport. If the option is available on your flight, pre-payment is taken during check-in on aa.com or in the app starting 24 hours and up to 4 hours before scheduled departure.