Linked from
The 12 pages that link to Glider, each with the reason it gives.
AircraftBroader topic: Gliders show that flight does not require an onboard engine.
AeronauticsBroader topic: Gliders reveal how aerodynamic efficiency and rising air sustain flight.
AerostaticsCompared with: Gliders rely on wing lift rather than displacement-based buoyancy.
Model aircraftBroader topic: Unpowered model gliders rely on rising air and efficient design.