I know this has been mentioned before around the forum but never its down thread. But basically, I wish there was a way where you have the choice to buy the planes your are leasing and not have to delete your flight schedule and release the plane and than pray to god that you can pick it back up and buy it before someone else grabs it on the market.
So long as your leasing from AS and not another player, after 4 weeks you get the option to buy the plane. Just go on the leasing page from the fleet management tab. The far right column gives you the option to buy the plane and shows how much it will cost you.