PS Seatcounter doesn't tell you how many seats are left. It tells you how many is left in each fare BUCKET, which does not necessarily relate to how many seats are left. Just like Southwest, if the low fare buckets are sold out, that generally means the flight is more full. But its still not an exact science. Airlines don't post this information publicly because it would give up a competitive edge if USAirways could write a robot script to see where Southwest is selling seats (ah hah! that flight to X is always full, maybe I should start service there). ETC.