Diversions feel random from seat 23C, but they follow patterns — six causes account for nearly all of them, and London's geography decides where the diverted end up. Knowing the patterns turns a bewildering night into a merely annoying one.
24/7 — diversions don't keep office hours
Fog is the classic — and it discriminates: London City's short, steep approach closes first, Heathrow and Gatwick hold longer. Crosswinds, snow and thunderstorm cells do the same job seasonally. The aircraft holds, burns its holding fuel, then commits to somewhere clearer — often Gatwick catching City's traffic.
A blocked runway, a drone sighting, an ATC systems failure — the destination itself goes offline and every inbound aircraft needs a new answer at once. These are the mass-diversion nights when three hundred people hit an unprepared forecourt together.
Delayed departures can arrive after their destination's night restrictions bite — and the flight lands where the rules allow instead. It's why so many diversions happen at exactly the hour onward transport has gone to bed: the 2am Stansted special.
A passenger emergency sends the aircraft to the nearest suitable airport, full stop. Technical cautions and fuel maths (holding eats reserves) do the same. These diversions are singular — one planeload, one unexpected city, and usually an airline scrambling a plan.
Long runway, spare night capacity, room to park widebodies — Stansted is London's designated catcher's mitt, hoovering up Heathrow, Gatwick and City's problems. Its own passengers occasionally get reverse-diverted to East Midlands when it saturates.
Heathrow's overflow lands at Gatwick and Stansted; City's fog traffic at Gatwick and Southend; Luton and Stansted trade Ryanair and Wizz arrivals. The inter-airport fare table exists because of this shuffle.
When the whole London system chokes — regional ATC failure, area-wide storms — flights scatter to Birmingham, East Midlands and Manchester, and the airline coach problem scales with the distance. Long-distance recovery is quoted in minutes on the master playbook.
The playbook, the who-pays answer and a fixed-fare car — all one link away.