u/indecisionmay

I ran a small real-world test on American Airlines (AA 5056, DCA-SYR) seat assignment progression over a 21 hour period. I bought the most basic economy fare; my seat would be assigned at check-in.

My theory was that checking in at T-24 hours might actually be worse if the system first assigns the cheapest, least desirable seats while holding better seats for sale. Since this aircraft is 2-2 with no middle seats, the downside of waiting was pretty limited.

The seat map evolved like this:

T-24: 8 undesirable $14 seats, 15 better $30-$36 seats
T-18: 4 undesirable, 15 better
T-6: 1 undesirable, 15 better
T-3.5: 0 undesirable, 11 better

So the cheaper seats disappeared first, while the more expensive forward and exit-row seats stayed protected much longer.

I checked in at T-3.5, right after the last cheap seat disappeared and the better inventory had started being used.

Result: 8A, the front-most available $30 seat, assigned for free.

Obviously one flight doesn’t prove AA’s algorithm always works this way, but it was a pretty clean example of why “check in exactly at T-24” may not always be the best strategy for Basic Economy, especially on an aircraft with no middle seats.