Editing Heathrow Airport (section)

===Arrival stacks===
{{main|Heathrow arrival stacks}}
Inbound aircraft to London Heathrow Airport typically follow one of several Standard Arrival Routes (STARs). The STARs each terminate at one of four different [[VHF omnidirectional range|VOR installations]], and these also define four "stacks"<ref name="UK AIP">{{cite web|url=https://www.aurora.nats.co.uk/htmlAIP/Publications/2021-10-07-AIRAC/html/index-en-GB.html|title=UK AIP – EGLL London Heathrow|publisher=NATS|access-date=1 November 2021|author=NATS|date=17 October 2021|archive-date=1 November 2021|archive-url=https://web.archive.org/web/20211101110928/https://www.aurora.nats.co.uk/htmlAIP/Publications/2021-10-07-AIRAC/html/index-en-GB.html|url-status=live}}</ref> where aircraft can be [[Holding (aviation)|held]] if necessary until they are cleared to begin their approach to land. Stacks are sections of [[airspace]] where inbound aircraft will normally use the pattern closest to their arrival route. They can be visualised as a [[helix]] in the sky. Each stack descends in {{convert|1000|ft|m|0}} intervals from {{convert|16,000|ft|m|0}} down to {{convert|8000|ft|m|0}}. Aircraft hold between {{convert|7,000 and 15,000|feet|m|0}} at 1,000-foot intervals. If these holds become full, aircraft are held at more distant points before being cleared onward to one of the four main holds.{{cn|date=July 2024}}

The following four stacks are currently in place:{{cn|date=July 2024}}
* The Bovingdon stack is for arrivals from the northwest. It extends above the village of [[Bovingdon]] and the town of [[Chesham]], and uses the VOR BNN ("Bovingdon"), which is situated on the former [[RAF Bovingdon]] airfield.
* The [[Biggin Hill]] stack on the southeast edge of Greater London is for arrivals from the southeast. It uses the VOR BIG ("Biggin"), which is situated on [[London Biggin Hill Airport]].
* The [[Lambourne]] stack in Essex is for arrivals from the northeast. It uses the VOR LAM ("Lambourne"), which is situated adjacent to [[Stapleford Aerodrome]].
* The [[Ockham, Surrey|Ockham]] stack in Surrey is for arrivals from the southwest. It uses the VOR OCK ("Ockham"), which is situated on the former [[Wisley Airfield]].

In high-traffic situations, air traffic controllers can opt to use a number of RNAV STARs either to send traffic to a non-standard stack or to move traffic from one stack to another. These are not allowed to be used for flight planning and will be assigned by ATC tactically.{{cn|date=July 2024}}