If you've ever watched a jet plane taking off or coming in to
land, the first thing you'll have noticed is the noise of the
engines. Jet engines, which are long metal tubes burning a continuous
rush of fuel and air, are far noisier (and far more powerful) than
traditional propeller engines. You might think engines are the key to
making a plane fly, but you'd be wrong. Things can fly quite happily
without engines, as gliders (planes with no engines), paper planes,
and indeed gliding birds readily show us.