Quota Count is a system used in the UK by London's Heathrow, Gatwick, and Stansted airports to limit the amount of noise generated by aircraft movements at night time (23:30–06:00).
From 1962 until 1993, operations at Heathrow were subject to a simple limit on the number of aircraft movements that were allowed to take place during the night period.
Each aircraft type is classified and awarded a quota count (QC) value depending on the amount of noise it generated under controlled certification conditions.
[7][full citation needed] Field measurements suggest the approach quota allocation for the A380 may be overly generous compared to the older Boeing 747.
[9] Subject to some limited carry-over provisions, when the airport's quota has been fully used up, no more night-time movements are allowed to take place.