Business aircraft are taking to the skies again as many economies around the world improve, but a surplus of jets delivered just before the recession means the equivalent of 2,750 jets remain parked in hangars. An excess of jets is depressing prices for planes, particularly older ones, and clouding the outlook for manufacturers of new jets, such as Bombardier Inc, Gulfstream and Cessna. Some companies are cutting back on corporate jet travel and reducing executives’ use of corporate jets for personal trips.