A plane's engines make thrust, a push that moves the plane forward through the air. Thrust comes from pushing gas backward: the engine pushes gas to the rear, and the gas pushes the engine forward. Some airplanes use propellers, instead of jets, to push them through the air. Turbofans work well on fast planes, and propellers are used on slower ones.

A jet engine takes in air, squeezes it with a compressor, burns fuel in it, and sends the hot gas through a turbine and out the back. The gas leaving the nozzle is faster than the air entering, and that makes thrust. The air enters through the front opening, called the inlet. The compressor squeezes the air to a much higher pressure before fuel is added and lit.

A turbofan engine splits the air into two streams: part goes through the core where fuel is burned and part goes around it. The ratio of the two is the bypass ratio. A turbofan has a big fan at the front, and both streams add thrust. Turbofans are fuel-efficient because the fan adds a lot of thrust while the core uses only a little more fuel.

Lift pushes a plane up, weight pulls it down, thrust pushes it forward and drag pulls it back: these are the four forces of flight. A plane needs enough lift from its wings to beat its weight, and enough thrust from its engines to beat its drag. The air pushes back against a moving airplane, and this push is called drag.

A plane has to move for its wings to make lift. A plane that is not moving through the air makes no lift. Lift only works where there is air, and with no air, wings make no lift. Planes that fly faster get more lift, and lift grows with the square of the plane's speed.

The Wright brothers, Orville and Wilbur, made the first flight of a powered airplane in 1903. The Wright brothers' first flight, on December 17, 1903, lasted only 12 seconds. The first flight of the Wright Flyer went 120 feet. They had tested gliders at Kitty Hawk for three years before they tried a plane with an engine.

In 1905 the Wrights flew their Flyer III almost 25 miles in 39 minutes, a flight in circles over Huffman Prairie near Dayton, Ohio. Only 65 years after the Wrights' first flight, astronauts walked on the Moon.

Words to know

• compressor: air squeezer
• turbine: spinning engine part
• nozzle: exhaust opening
• turbofan: engine with fan
• inlet: front opening