Air travel around London is a mess today. The airspace over the city was briefly closed in the afternoon because of what authorities said was a computer failure at one of Britain's two air traffic control centers. NATS, Britain's national air traffic body, said the glitch at its center in Swanwick, England, had been resolved, but the effects were expected to ripple as normal operations resumed. Exactly what happened remains unclear, though officials at London Heathrow cited a power failure.
The shutdown came at the start of the weekend in a sprawling city with five commercial airports, including Heathrow—Europe's busiest— as well as Gatwick, Luton, Stansted, and London City Airports. Heathrow alone handles about 1,200 to 1,400 flights a day, about 200 of those to and from the United States, according to the flight tracking service FlightAware.