Three flights were diverted from Gatwick Airport because of "IT issues" in the air traffic control tower.
Flights from Tampa, Antigua and Belfast are believed to have been affected by the problems this morning.
Passengers on social media have reported landing at Heathrow amid confusion over what happens next.
A Gatwick Airport spokesperson said the diversions were the result of "IT issues in the air traffic control tower this morning".
They later added: "Earlier IT issues in the air traffic control tower this morning have been resolved and flights are arriving and departing as normal.
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"Some flights may still experience delays however and passengers are advised to check their flight status with the airline."
Two British Airways flights were diverted to Heathrow Airport, it has been reported.
One EasyJet flight was redirected to London Luton Airport, a spokesperson for the airport later confirmed.
Flight radar tracking showed a number of planes circling above Gatwick..
Some passengers took to social media to say the airport is currently a "shambles" due to long queues.
Gatwick Airport's Twitter account confirmed things were back to normal.
But they did say flight delays were now possible - and told passengers to check before setting off.
"Earlier IT issues in the Air Traffic Control tower this morning have been resolved and flights are arriving and departing the airport as normal," they said on social media.
"Some flights may still experience delays and we advise you to check the status of your flight with your airline."
While arrivals were blocked from landing, a number of departures have also been delayed at Gatwick this morning.
The first nine flights of the day - all EasyJet departures to European destinations - were delayed by at least an hour, with some departing more than two hours late, it was reported.
