How do sailplanes (gliders) stay aloft?
Gliders are usually towed to altitude by a motorized airplane and then use rising air from natural weather phenomenas such as thermals, mountain lee waves or ridge lift to stay aloft.
Instruction: How do sailplanes (gliders) stay aloft?
Context: 
Response: Gliders are usually towed to altitude by a motorized airplane and then use rising air from natural weather phenomenas such as thermals, mountain lee waves or ridge lift to stay aloft.