Gatwick Airport says flights have been suspended due to an “air traffic control system issue” in the control tower.
Outbound and inbound flights will be delayed until at least 9pm, according to the Eurocontrol Netowrk Operations Portal.
A statement from Gatwick says: “Due to an air traffic control systems issue in Gatwick’s control tower, flights are currently suspended. We are working with ANS, our air traffic control provider, to rectify this issue as quickly as possible.
“We apologise and passengers should check with their airline directly or on our website flights page for the latest information on their flight.”
The issue began at 5.08pm on Wednesday afternoon.
The airport say there is already a divert plan in place, and inbound flights are being sent to other airports.
Gatwick, in West Sussex, is Britain’s second busiest airport, behind Heathrow.