Why "as the crow flies" is no longer the real flight distance from London
Since most Western airlines stopped overflying Russian airspace in 2022, routes from London to destinations like Tokyo or Seoul have grown by roughly 2-3 hours compared with the great-circle distance this calculator gives, because planes now divert south over the Middle East or Central Asia. The Haversine distance is still the correct geometric answer, but it is worth knowing that the airline's actual routing can add hundreds of extra kilometres on certain long-haul routes from the UK.
Nautical miles, still used in UK aviation and shipping
While this tool gives distance in kilometres and miles, UK pilots and mariners work in nautical miles (1 nm = 1.852 km), based on one minute of latitude. If you are converting a distance for aviation or maritime purposes rather than general travel, divide the kilometre figure by 1.852 to get the nautical mile equivalent.