Definition
Airplanes with a maximum certificated takeoff weight of more than 300,000 pounds, whether or not they are operating at that weight on a particular flight. In ATC communications, these aircraft use the word 'Heavy' after their call sign because they generate strong wake turbulence that affects spacing requirements for following traffic.
Plain English
Large aircraft certified to take off at weights above 300,000 pounds. They are called 'heavy' on the radio because the swirling air they leave behind their wings is strong enough that other aircraft need extra distance to stay clear of it.
Context Anchor
You will see this term in airport traffic pattern and runway-use discussions, especially when spacing smaller airplanes behind larger ones.
Derivation
Heavy comes from Old English words meaning weighty or hard to lift. That helps here because aviation uses the idea of weight in a practical way: a heavier airplane generally needs more room and creates a stronger effect on the air around it.
Why Pilots Care
Following or preceding a heavy airplane requires greater spacing to avoid wake turbulence that can roll a smaller aircraft.
Intuition Check
Do not read heavy airplanes as simply airplanes carrying a lot of passengers or baggage. Here it refers to the airplane’s approved size and weight class, not how loaded it happens to be on one flight.
Example Sentence 1
The tower called, 'Cessna 12345, caution wake turbulence, heavy 747 departing Runway 27.'
Example Sentence 2
Heavy airplanes fly wider traffic patterns because of their higher speeds and larger turn radii.