That is strange, will have to look into that. It should spawn at the saved altitude. I know this works because I have used it after CTD to respawn in the air where I was at the CTD (unfortunately, it starts in a dive, but I can usually recover, working on that).
It would be difficult to spawn at the airport elevation, because different points at the airport could have very different elevations.
I have seen it spawn right on top of other planes and others have reported it, so I know that it is an issue