Definition
An aircraft classified by the FAA as having a maximum certificated takeoff weight of more than 300,000 pounds, whether or not it is operating at that weight on a given flight.
Plain English
A large airplane officially rated to take off at more than 300,000 pounds. The label is based on what the aircraft is certified for, not how much it actually weighs that day.
Context Anchor
You will see this term in wake turbulence, wingtip vortex, takeoff, landing, and air traffic control spacing discussions.
Derivation
Heavy comes from the everyday sense of great weight. In FAA usage it specifically flags aircraft by takeoff weight because they generate the strongest wake vortices.
Why Pilots Care
Following aircraft must use greater separation distances or times after a heavy to avoid hazardous wake encounters.
Grounding Statement
Picture a large jet taking off ahead of you: the heavier it is, the harder its wings are working, and the stronger the spinning air it may leave behind.
Intuition Check
Heavy does not only mean “loaded with passengers or bags today.” In FAA wake-category use, Heavy refers to what the aircraft is certified to weigh at maximum takeoff, whether or not it is that heavy on a particular flight.
Example Sentence 1
The tower instructed the small jet to extend its downwind to allow extra spacing behind the heavy aircraft on final.
Example Sentence 2
Light aircraft pilots watch carefully when sequenced behind a heavy aircraft on approach.