Gatwick Airport has reopened its South Terminal after a “large part” of it was evacuated and a bomb disposal team was called.
The discovery of a “suspected prohibited item” in a passenger’s luggage triggered the emergency response.
Explosive experts were deployed to the terminal “as a precaution,” Sussex Police said, as the force warned the response was “causing significant disruption”.
Follow disruption latest: Gatwick Airport evacuation ends
Read more: What are your rights if your flight is affected?
Earlier the airport, which is the UK’s second busiest, said the terminal was evacuated after a “security incident”.
“The earlier security alert has now been resolved and cleared by police,” it later said in a statement on Friday afternoon.
“The South Terminal is reopening to staff and will be open to passengers shortly.”
Gatwick said some flights were cancelled while others were delayed.
It said passengers should contact their airlines for any updates on flights.
Footage on social media taken outside the airport showed crowds of travellers heading away from the terminal building.
“Arrived at London Gatwick for routine connection. Got through customs to find out they’re evacuating the entire airport,” one passenger said.
“Even people through security are being taken outside. Trains shut down,” another passenger added, who said “thousands” of people were forced to leave.
Another passenger said people near the gates were being told to stay there and not go back to the departure lounge.
People outside the airport were handed blankets and water, passengers told Sky News.
The airport said its North Terminal was still operating normally.
Gatwick Express said its trains did not call at Gatwick Airport during the police response, but the airport said trains would start calling there again once the terminal was fully reopened.
More than 600 flights were due to take off or land at Gatwick on Friday, amounting to more than 121,000 passenger seats, according to aviation analytics firm Cirium.