Okay I'm having this problem with the aircraft taking off... seems like the selection boxes sink whenever they are created or land, and so the aircraft have to wait for those selection boxes to sink, the particle bones look as if they are lower to the ground, and when the unit takes off it suddenly sinks to the ground. Take a look at these images in sequential order:
Are aircraft supposed to be in the very middle of Z axis? Is that related to this problem? Does MinHeight have something to do with it?