Normally the only reason to ascend and descend is to take off and land (at least in the civilian world). Take offs and landings are hard on a airplane but the hardest thing on an airframe is setting, believe it or not. They are made to fly and no airplane can set long and survive. I know I use to fly for living. ( I use to do a lot of things for a living). And Air Force One has all the nice stuff on it you could dream of, I use to know some former crewmembers of Air Force 1. I just can't see them using a foreign airframe for such a high profile airplane. I've heard some people say "If it ain't Boeing I ain't going." And considering the quality of some of their older aircraft I can understand why. More redundans systems than you can imagine and overbuilt. They make some great aircraft.