What is wake turbulence?
Large aircraft leave swirling air behind them, so controllers keep a gap between aircraft to keep everyone safe.
What causes it
Lift on the wings creates two spinning tubes of air that trail from the wingtips. They sink slowly and can last for a minute or two. The bigger and heavier the aircraft, the stronger they are.
Why you hear “Heavy”
Aircraft are grouped by weight. The biggest, such as the Boeing 747 or Airbus A380, are the heaviest groups, and controllers add the word “Heavy” or “Super” to their callsign on the radio as a warning to others.
What controllers do about it
They keep extra distance or time between a large aircraft and a smaller one following it. That is one reason you sometimes see a gap after a big jet before the next one is cleared to take off.
Watch for it
After a very large aircraft takes off or lands, look at how long the runway stays empty before the next one goes.