Originally Posted by Blumie
Today I experienced something which I found to be a little unusual, but is yet further evidence that seatmaps cannot be relied upon. I booked myself on AA4618 JFK-BOS for one afternoon next week (I won't tell you which day: I don't need any of you jokesters -- brp -- to go and cancel my reservation!). Expertflyer showed the flight at Y2, which most know means that AA is willing to sell exactly two more seats on this flight, and probably means that the flight is (or will be once these last two seats are sold) oversold. The seatmap, however, showed 13 of the 37 seats as available. Someone relying on the seatmap might conclude that the flight is wide open and they would, of course, be completely wrong.
This is pretty obviously the result of people with reservations not having reserved seats. In the case where the seat map is full, however, it really does suggest something more useful (while not being fully reliable). If the F or J cabin seat maps are completely full, those cabins are full (since there are no seat blocks for airport allocation). And they usually won't oversell the premium cabin (they'll oversell J internationally, I expect).