Passengers travelling from Heathrow and Gatwick faced more delays on Friday due to a technical hitch at air traffic control.
A faulty radar is believed to be to blame for the delays, which are affecting thousands of passengers.
Flights were operating at both airports, but the UK’s air traffic control service NATS had to reduce capacity due to the fault.
The problem was at Swanwick, the main control centre for southern England.
Passengers were already facing delays due to overnight thunderstorms, which caused some flights to be cancelled and others were postponed.
In a statement at 3pm NATS said the problems were resolved and said it could safely increase traffic flow rates, but it warned that adverse weather was continuing to cause disruption across the UK and more widely across Europe.
