I am noticing seats appearing and disappearing on several routes lately. In booking seats to/from YWG this week the flights I wanted initially were sold out for my T+ Pass. When i went back in to check yesterday the flights showed seats available in classes as low as Q which is frustrating as AC charges $50 to change if you've held a seat on another flight for more than 2 hours on a T+ pass. I clearly understand that people change flights which changes inventory. AC does oversell but not to pass holders. Comments?