Depends on the technology. The failure mode for a lot of aircraft is that they simply glide to the ground. Even helicopters / autogyros do something similar - there's still a lot of momentum in the rotors and you sycamore down to the ground. It's not like the antigravity suddenly fails and you're back to having weight again.
When I was learning to fly, engine failure was one of the things that I had to practice a lot. Engine failure immediately after takeoff is potentially dangerous, because you don't have an engine and you don't have enough speed or altitude to go very far. You typically have to land in a field (or, if you don't want to damage your aircraft in a training exercise, you throttle the engine back and feather the prop, then line up your emergency landing and turn the engine back to maximum late in the approach so that you stay in the air).