Passengers at Luton Airport were left facing border control queues up to two hours long overnight, due to an IT glitch.
The problem, which also affected travellers arriving at Heathrow, Gatwick and Stansted airports, meant that UK Border Force staff had to manually input passport details for those arriving in the UK rather than scan documents.
The glitch caused a large backlog at London Luton, with reports that it took two hours for travellers to be processed.
Passenger Simon Kalman, who arrived at Luton from Barcelona at 10.45pm last night, told BBC News he was forced to wait alongside around 2,000 other people.
He said: “It was a total mess, there was limited water available and people were getting very frustrated.”
Josh Bone captured the madness at 1am this morning, in a picture which shows hundreds in line.
At the time he added: “Sort it out”.
Immigration and Security Minister James Brokenshire apologised for the problem.
He said: “Our engineers have been working through the night to fix the temporary IT problems that regrettably led to longer queues for some passengers at passport controls yesterday.
“The current situation is much improved and we are doing our best to keep waiting times to a minimum during this morning’s busy period.
“We apologise for any delays but security must remain our priority at all times.”