This happens on both a dedicated server (with a ping around 40ms) and a non-dedicated server (0 ping).
Sometimes, you can get unstuck with just thrust (not often). Our current solution is to pop the plane up .2 meters with a setPosATL and add some forward velocity of about 2m/s with setVelocity. This works (not all the time, but spam it and you will get unstuck). The only downside is that it damages the plane so I need to make it undamageable during the pop.
das