What is subsonic speed? As British Airways flight to Heathrow Airport comes close to speed record - how does it compare to speed of sound?

British Airways Boeing 747 flight 274, an Airbus A350, reached a ground speed of 814mph and shaved 45 minutes off its journey from Las Vegas to Heathrow on Wednesday (22 January), according to flight radar records. The record for subsonic speed is 835mph and the typical cruise speed is about 600mph.

Jet streams are fast-moving winds that flow about 30,000ft above the Earth’s surface and blow across the Atlantic to the UK. Airlines use the winds to save fuel between the United States and Europe and they are also why it is faster to fly in that direction than the other way, though flights propelled by jet streams may experience more turbulence.

The subsonic record was set in 2020 on a New York to London flight that lasted only four hours and 56 minutes, two hours and four minutes faster than the average journey time for that route. Experts have said a record may be set in the coming days thanks to the unusually fast north Atlantic jet stream.

Other flights have come close recently. This week a Qatar Airways flight from New York to Doha reached 833mph and landed about 50 minutes early.

The speed of sound is 760mph, but in these instances the aircraft ground speeds are not classified as supersonic because they were still flying at typical cruising speeds relative to the air. The record for the fastest commercial transatlantic flight was set in 1996 by a British Airways Concorde, which flew from John F Kennedy airport in New York to Heathrow in two hours, 52 minutes and 59 seconds.

The news comes as Storm Eowyn has broken records in Ireland after 114mph winds hit the island, the fastest since records began, the Irish forecaster has said. Gusts of 183kmph were recorded at Mace Head, County Galway, at 5am on Friday (24 January).