U.K. airports and airlines said they are working to get their operations back to normal, after a technical issue at the country's air-traffic-control system led to extensive flight groundings.

More than 2,000 flights to and from the U.K. were affected between Tuesday and Wednesday, according to data provided by aviation analytics company Cirium.

Roughly 30% of U.K. flights scheduled for Tuesday either were canceled or didn't fly, and around 5% of those due Wednesday have been canceled so far, according to Cirium. On a normal day, the cancellation rate ranges from 1% to 2%, it added.

Air-traffic-control group NATS Holdings said Tuesday that it had identified a technical issue in its flight-processing system that disrupted departures. The company said during the European evening it had resolved the issue and was working to clear the backlog of flights.

British Airways said Wednesday it canceled more than 190 flights as crews and planes were out of place after the NATS outage.

Germany's Lufthansa Group also had to divert or cancel certain flights to and from the U.K. due to the disruption, according to a company spokesman. The restrictions occurred on Tuesday, but flight operations ran without further disruption as of the European afternoon Wednesday, the spokesman added.

A spokesman for easyJet said there were a small number of aircraft out of position on Wednesday and a few flights from the U.K. were affected, but that the airline was operating as planned.

Budget airlines Ryanair and easyJet criticized NATS following similar outages in recent years.

The NATS technical issue prompted airlines to cancel hundreds of flights and affected the travel plans of tens of thousands of passengers, easyJet Chief Executive Kenton Jarvis said.

"Despite assurances that lessons had been learned, customers are once again bearing the brunt of NATS' shortcomings," Jarvis said.

Ryanair's CEO Michael O'Leary said in a statement that the NATS CEO Martin Rolfe should be removed from his role after issues with the group's air-traffic-control systems.

In response, a spokesperson for NATS said it acknowledges the significant disruption experienced by airlines and passengers, adding it has an immediate focus on the recovery of the aviation network.

Several U.K. airports said they were trying to restore their services but warned that the recovery might take time, while others said their operations were back to normal.

London's Heathrow Airport said on X that while flights were operating Wednesday some disruption might continue as airlines reposition aircraft and crew.

"Flights have now resumed from London Gatwick," the airport said on X. "However, we still anticipate that it will take time for our operations to fully return to normal."

Meanwhile, Manchester Airport said it was operating as normal.