Regional or local Air Traffic Control centres guide most aircraft in the sky.
A formation
Gas comes out of airplanes, which causes air pollution, and sometimes changes the sky color.
Airplanes were built for flying and transportation purposes.
They fly.
Flying in airplanes: up to scratch idea
In 1903.
The sky
there is bob flying one and bill
1920
safety service
He liked flying airplanes.
Flying in airplanes... He takes the train...