Birmingham Airport said it was “slowly returning to normal” after its terminal was evacuated over a suspicious vehicle.
Many flights were grounded and people told to leave the airport building while a police operation got under way at about 12:20 BST.
An Explosive Ordnance Disposal (EOD) team searched the vehicle which was “deemed to be safe”, West Midlands Police said.
An airport spokesperson apologised for “any inconvenience and disruption” but said “the safety and security of everyone at the airport was our number one priority as we worked through this incident with police partners.”
The evacuation affected passengers who were checking in for the flights, with a police cordon set up around the airport and people advised not to travel to the airport.
The BBC understands passengers who had cleared security were permitted to go through to departures as they were deemed safe.
In their latest update, an airport spokesperson said: “Birmingham Airport is working closely with its airline partners to minimise any potential disruption to customers.
“The majority of flights that were held on the ground have now departed, with only one cancelled flight.
“Customers are still advised to check their flight status with their airline.
“We again apologise for the inconvenience to our passengers but their safety and security is our priority.”
Travellers posted their frustration on social media at being left on planes that had just arrived at the airport.
One user on X, @harmancheeta, said they were “stuck on a plane, claustrophobic, pleading to get off,” and asked: “How long is this situation going to take?”.
Another, @SpandleRandle, said his mum and dad were also on a plane at Birmingham Airport after returning from Spain and had “no idea what’s going on”.
Some were not happy with the way the disruption was handled.
Passenger Samia Khan said there were “no updates, nobody telling us what was going on, it’s just absolutely ridiculous”.
“I could have easily just caught the train to Amsterdam and I’m probably going to opt for that next time, because flying’s just been made so difficult with all the delays,” she said.
“Birmingham Airport could have just dealt with the whole situation much better.”
Ian Pugh posted a photo of crowds outside the building.
“It seemed very busy and the numbers of people just started growing,” he said.
“At first I just thought it was people going to the train station and maybe the monorail had failed but the numbers just got larger.”
Some passengers were asked to assemble at the nearby National Exhibition Centre (NEC).
West Midlands Fire Service and West Midlands Ambulance Service both had crews on site while the investigation took place.
Passengers were allowed back into the airport from 15:30 BST.
Birmingham Airport was also evacuated in September, when travellers were temporarily asked to leave a small area in the arrivals zone.