Flights at Gatwick Airport were suspended for about two hours due to what it says was an issue in its control tower.
A total of 25 flights were diverted to other UK airports when the problems began shortly after 17:00 BST.
The airport said it had experienced a problem with its air traffic control systems.
Passengers due to travel to or from the airport have been advised to check for updates with their airline.
Gatwick Airport says flights have now resumed in a statement on Twitter:
Following an earlier air traffic control systems issue, flights to and from Gatwick have now resumed.
If you are travelling this evening please check the status of your flight with your airline before travelling to the airport, as we return to full operations.