A fault with security scanners early yesterday left hundreds of travellers stranded for hours at Stansted.
Passengers posted photographs of large crowds inside the terminal building on social media, with one describing the scene as “a huge pile-up”.
There were reports of delays of more than two hours in the departure lounge – with some missing flights altogether.
The airport apologised and said a “technical issue” had hit the scanners.
Extra time was needed to process passengers as a result, and those who missed flights were getting help rebooking, a spokesman said.
The problem with the hand baggage X-ray machines emerged at about 4.30am yesterday, with many frustrated passengers taking to social media to complain about missd flights.
Passenger Meagan Tetro tweeted: “Hundreds stranded at Stansted Airport due to their system failing. All missed flights and now stuck queuing.”
She said she was with about 150 other people needing new flights, and described the situation as an “embarrassing show of service” from the airport and Ryanair.
She added that it could be 18 hours before the next available flight.
A Ryanair spokesman said the airline regretted any inconvenience but added it was “not responsible for airport security delays”.
An airport spokesman told the BBC: “Due to a technical issue with a number of X-ray machines in the main security area, throughput capacity was reduced, taking extra time to process passengers.
“Engineers rectified the issue and additional measures were put in place to minimise the impact to passengers. We apologise for the inconvenience caused.”