Understanding why flights are disrupted at Heathrow is critical because not all delay causes exempt the airline from paying compensation.
1. Runway Congestion and Slot Restrictions
Heathrow operates at 98% runway capacity with only two runways serving all traffic. This creates a bottleneck effect where a small delay in one departure can cascade through the entire schedule.
Claim impact: Runway congestion is an operational issue — airlines are responsible for building buffer time into their schedules. Claims based on slot restrictions are frequently successful.
2. Fog and Adverse Weather
Heathrow experiences reduced visibility (fog, low cloud) primarily from November through February. During heavy fog events, the airport switches to Low Visibility Procedures (LVPs), which reduce landing rates from 45 to around 28 per hour.
Claim impact: Genuine fog delays are considered extraordinary circumstances. However, airlines often list "weather" as the cause when the actual delay was partly or fully operational. We investigate the METAR weather data for your specific departure time to verify whether fog was truly the cause.
3. Technical Faults and Aircraft Defects
Aircraft technical issues — from avionics failures to hydraulic leaks — account for a significant share of Heathrow delays. Under EU/UK261, technical problems are not extraordinary circumstances (confirmed by the Wallentin-Hermann ruling, C-549/07).
Claim impact: Technical fault delays almost always qualify for compensation. Airlines cannot use "safety checks" or "routine maintenance" as an excuse.
4. Inter-Terminal Transfer Delays
Heathrow's four terminals are spread across a large campus. Transfer passengers moving between Terminal 5 (British Airways hub) and Terminals 2–4 must use the Heathrow Express or bus services. Delays in these transfers can cause missed connections.
Claim impact: If your connection was missed due to insufficient transfer time scheduled by the airline, the carrier is liable for compensation. This is a single-booking, single-journey rule — both legs must be on one ticket.