Around 150 people were forced to spend the night wrapped in blankets at Gatwick after a security alert closed the North Terminal.
The terminal was evacuated after a live hand grenade was found on a plane with 125 passengers on board.
A 37-year-old man was stopped by Customs officers in the green channel after arriving on British Airways flight 2048 from Bogota, Colombia.
The man, who is understood to have boarded the flight at Caracas, Venezuela, was taken to a central London police station where detectives from Scotland Yard’s Anti-Terrorist Branch were questioning him today.
Terminal manager Christine Gover said that from around 2pm yesterday all but nine British Airways flights from the North Terminal were cancelled.
As a result passengers on more than 30 flights had to be rebooked on to flights today.
Although some people spent the night in a hotel, many slept on sofas, chairs and any space they could find on the floor last night.
Ms Gover said: “Gatwick Airport handed over blankets and drinks to people overnight. We estimated there are about 150 people that spent the night in the terminal.
“There are queues for people to get tickets for flights today and there are also queues because we already had a busy day ahead and with yesterday’s passengers all the flights are full this morning.
“We are actually back to normal. In terms of clearing the backlog of people, I envisaged that could go on for most of the morning.”
When Sara Crowe, 19, arrived at Gatwick in the early hours of the morning for her flight to Australia later today, she found a sea of people sleeping all over the terminal.
She said: “When we arrived there were loads of people asleep. There were people all over the place. They have gone now.
“Everyone had blankets. It was quite quiet. They were even sleeping on the floor.”
The Okacha family arrived early for their flight to Tunisia because of the terror alert yesterday.
From 1.30am they joined the people who had gone to the arrivals lounge to find a place to sleep.
Jayne Okacha, from Islington, North London, said: “Because all the seats were full we went down to arrivals to sleep. It was freezing but they handed out these special foil blankets and came round with water. There were not enough spaces to sleep in the warm, but this morning our flight is okay.”
She said the atmosphere was calm and very peaceful although her daughter Layla complained of waking up with neckache.