How reliable is London Heathrow?
Flights from LHR avoided significant airline-controlled delay in 69% of 1,148,590 flights in official UK CAA history — and weather is calmest in Jul. Here’s the full picture before you book.
Reliability score
on-time, cancellations & delays
Weather favorability
year-round climate
Origin-airport operations
What the airline-controlled delay record at LHR looks like
Avoided 15+ min controlled delay
across 1,148,590 flights
Source: UK CAA · data through 2026-06-25. Origin-grouped, cause-attributed operational history; it is not a direct departure-punctuality measure or a guarantee for any flight.
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Weather by month
When the weather works for you at London
A calm-weather score (0–100) for each month from decades of airport observations — how often conditions disrupt flying, not temperature. Higher is calmer.
Calmest month
Calmest flying weather of the year · 99/100 favorability
Roughest month
Most disruptive — low visibility & fog, high winds · 93/100 favorability
Connecting through LHR
How much layover you really need
Allow at least this between domestic flights at LHR. Below it, one small delay risks a misconnect.
International transfers add immigration and bag recheck — give yourself this buffer at LHR or more.
PlaneSane connection-time estimate tuned for LHR's terminal layout. We score every connecting itinerary against conservative connection floors.
The read on LHR
What the numbers say about flying through London Heathrow
Across official performance history, flights from London avoided significant airline-controlled delay about 69% of the time over 1,148,590 flights. That's a middling record — neither a strength nor a red flag on its own. Pair it with a moderate cancellation rate of 1.6%. When a departure does run late, the typical delay is around 17 minutes.
On weather, London is an unusually calm-weather airport year-round. July is the calmest stretch for flying, scoring 99 out of 100 for favorable conditions, while December is the most disruptive at 93, driven mainly by low visibility & fog and high winds. The year is relatively steady, so no single month stands out as one to avoid on weather alone.
If you're connecting through LHR, give yourself room. A domestic connection wants at least about 75 minutes, and international transfer wants roughly 90 minutes once immigration and a bag recheck are in the mix. Those are floors, not comfortable buffers — one inbound delay can erase them, so add margin when the connection matters.
None of this guarantees your specific flight — it’s the backdrop. To turn it into a booking, score real flights to London, read how we weigh it all in how the PlaneSane Score works, and brush up with how to pick a reliable flight and avoiding weather delays.
Common questions about LHR
- How reliable is London Heathrow (LHR)?
- Flights from London avoided significant airline-controlled delay roughly 69% of the time across 1,148,590 flights of official history — a middling record — neither a strength nor a red flag on its own. The cancellation rate runs about 1.6%. It's advisory context, not a guarantee for any single flight.
- What is the best month to fly from LHR for good weather?
- July has the calmest flying weather at London Heathrow. December is the most disruptive, mainly from low visibility & fog and high winds.
- How much layover time do you need at LHR?
- Allow at least about 75 minutes for a domestic connection and about 90 minutes for an international one as a floor. These are minimums, not comfortable buffers — a single inbound delay can wipe them out, so add margin when you can.
Planning a trip through London?
Score real flights to and from LHR on reliability, weather, and connection safety — not just price.