Which of our 19 airports cancel and delay most, from official data only. US figures are from the Bureau of Transportation Statistics (BTS) for September 2025 to August 2026. Heathrow figures are from the UK Civil Aviation Authority (CAA) for calendar 2025. On time means the flight arrived or departed less than 15 minutes after the scheduled time.
How to read this. The headline figure is arrivals on time: the share of scheduled arrivals that reached the gate less than 15 minutes late. Cancellations count as not on time. Average delay is the average lateness of delayed flights only, so it is much higher than the average delay across all flights. Worst and best months are averages for that calendar month across every year since January 2022, computed from BTS on-time reports, so they show the seasonal pattern rather than one bad month. July is the worst month at 14 of the 18 US airports; the exceptions are DFW and SFO (June) and SEA and PDX (December).
Heathrow is measured differently. The CAA reports arrivals and departures combined, on time meaning early or up to 15 minutes late, so the LHR figure is not directly comparable with the US arrival and departure figures. In 2025, 76.75% of Heathrow flights were on time, up from 67.33% in 2024, and 1.32% were cancelled. Its worst month was September 2025, when departures averaged 17.3 minutes late; its best was April 2026 at 8.0 minutes.
Two US airports use a different source. The BTS TranStats airport pages for Atlanta (ATL) and Las Vegas (LAS) are not indexed in search, so their figures come from FlyingOver’s analysis of the same BTS reporting-carrier flight-level data for the same period, September 2025 to August 2026. Every other US airport links to its BTS TranStats page.
National picture. Across all US airports, 75.6% of arrivals were on time in this period. The worst single month was July 2026 (69.4% on time, 2.6% cancelled) and the best was September 2025 (82.8% on time, 0.5% cancelled). The biggest cause of delay minutes was late-arriving aircraft (39.8%), ahead of airline causes (32.9%). Flights scheduled 6 am to 7 am left on time 90.2% of the time; flights scheduled 8 pm to 9 pm managed 62.7%. Sources: BTS TranStats, UK CAA flight punctuality statistics, FlyingOver analysis of BTS data, AirDelay worst-months analysis of BTS data.