India, Sept. 8 -- Nearly 300 flights were cancelled on Tuesday after air traffic control provider NATS experienced a technical issue, with Heathrow, Gatwick, Manchester and Stansted among the hubs affected by cancellations and delays, according to flight-tracking website Flightradar24.

"We have identified that the issue was in our flight processing system. Our engineers are on site and working urgently to resume normal operations as quickly as possible. We recognise the ongoing disruption to travel, for which we sincerely apologise," NATS said in a statement.

"Flights are still departing and airspace is open, but recovery will take some time," it added.

Flightradar24, a website that tracks flights, said on social media that the problem...