Best time to fly London to Tokyo

Every month pooled across the years on record, so "July" means July generally rather than one particular July. Full LHR to HND record →

Best month

November

92.5% on time · 133 flights

Worst month

July

58.4% on time · 156 flights

Month Flights On time Cancelled When late, by
January 253 84.1% 0.79% 0 min
February 238 87% 0% 0 min
March 279 81.1% 1.43% 0 min
April 301 86.3% 0.66% 0 min
May 310 81.3% 0% 0 min
June 300 77.2% 2% 0 min
July 156 58.4% 1.28% 0 min
August 156 67.7% 0.64% 0 min
September 151 65.3% 0.66% 0 min
October 151 80.1% 0% 0 min
November 133 92.5% 0% 0 min
December 137 85.3% 0.73% 0 min

What a seasonal pattern can and cannot tell you

Months differ for reasons that repeat — summer thunderstorms in the American interior, winter fog and de-icing in northern Europe, school holidays filling every seat and leaving no slack in the schedule. Those are real and they come back each year.

What the pattern cannot do is forecast a particular flight. A quiet month has late days and a bad month has punctual ones. Treat this as a way to choose between two dates you are indifferent about, not as a promise.