All departing flights out of two of London’s largest airports, Heathrow and Gatwick, were grounded on Wednesday afternoon, according to representatives for the airports.

A spokeswoman for Gatwick Airport said the disruption was because of a technical issue with its radar. Inbound flights were still landing, but outbound flights were grounded. NATS, a company that provides most air traffic control services for the UK, said in a statement on social media that “a technical issue” at its air traffic control system had forced it to limit the number of aircraft flying in the London area.

“Our engineers are working hard to resolve the problem as quickly as possible and we are working closely with airlines to help minimize disruption,” the statement said. “At this stage we cannot say how long it will be before operations are back to normal.”

By 4.30pm (9pm IST), the company posted again on social media that the problem had been fixed. “Our engineers have now restored the system that was affected this afternoon,” the company wrote.