Start it out as a lighter than air dirigible, float it up high and fire the plasma jets, shrink the cross section diameter and deploy lift wings the faster it goes. When you want to land kill the jets, re-inflate and retract the wings, and float to the ground.
Freegards
Re-inflate? How? It's not like a sub, where the buoyancy medium surrounds you and you can pump it in or out at will. A heat source for hot air, maybe?