Wind tunnels are machines in which objects are held stationary inside a tube, and air is blown around it to study the interaction between the object and the moving air. They are used to test the aerodynamic effects of aircraft, rockets, cars, and buildings. Different wind tunnels range in size from less than a foot across, to over 100 feet (30 m), and can have air that moves at speeds from a light breeze to hypersonic velocities.
NASA wind tunnel with the scale model of the MD-11 wide-body airliner
16-foot supersonic wind tunnel at Arnold Air Force Base, 1960
A model Cessna with helium-filled bubbles showing pathlines of the wingtip vortices
Replica of the Wright brothers' wind tunnel
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or the dynamic lift of an airfoil, or, in a few cases, direct downward thrust from its engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors, and hot air balloons.
The Cessna 172 Skyhawk is the most produced aircraft in history.
Hot air balloons
Airship USS Akron over Manhattan in the 1930s
An Airbus A380, the world's largest passenger airliner