A suspicious vehicle that led police to close Liverpool John Lennon Airport has been removed for examination.
Airport shuttle buses were used to transfer people during the alert
The airport was closed for more than eight hours leaving hundreds of passengers stranded. It was reopened in the early hours of Sunday.
However, a number of flights on Sunday morning were cancelled and travellers were urged to contact their airline before starting their journeys.
The alert came hours after a burning car was driven into Glasgow Airport.
Other airports across the country have stepped up security following the attack.
In a statement, Merseyside Police confirmed the airport was re-opened at about 0440 BST on Sunday.
It said: "A vehicle has been removed from the airport and taken away for forensic testing.
"Customers hoping to use the airport are advised that they should contact their airline to confirm whether their flight will be going ahead."
Scores of people were stranded on three planes which landed moments after the airport was closed at about 2030 BST on Saturday.
City centre incident
But they, along with people who were in the terminal buildings, were taken to local leisure centres, a Liverpool City Council spokesman said.
He said airport shuttle buses were used to transfer between 400 and 500 people to the Austin Rawlinson and Garston centres.
Police said cordons around the airport had been lifted
"People were obviously a bit frustrated but recognised that these things happen," he said.
Salvation Army volunteers provided blankets and refreshments, but many people had been picked up by relatives or found a hotel room for the night.
Meanwhile police also closed part of Liverpool city centre for about two-and-a-half hours because of what they described as an "incident".
An area near Lime Street station was cleared and the Adelphi Hotel was evacuated, according to eyewitnesses.