Pilot software except vPilot, SquawkBox, FSInn and XSquawkbox
By Andreas Fuchs 810809
#530281 Swift, the new pilot client (currently in beta test phase) brings all aircraft to the same level as the player's airport/ground elevation.
By Magnus Meese 997444
#530308 Guessing this is xSquawkbox. There's a lot of floating going on with it, because A, it doesn't correct for it; and B, the other users will not only potentially be on FSX/P3D with different elevations, but since XP offers non-flat aerodrome surfaces as an option, 50/50 of XPers around you will be on completely different elevations as well.

The next version of xSB is said to include ground elevation correction. When it arrives is anyone's guess. The latest progress update came out last July.
By Andreas Fuchs 810809
#530310 In Swift, this problem has been solved:

Image

PS: you can see one aircraft, an Iberia CRJ900, "eating dirt". Explanation: this pilot had just connected when I took this screenshot, before Swift moved it to the correct altitude.