A glitch in a computer system used to check in passengers for flights has left a number of major airports around the world in a state of disruption.
Issues have hit London's Gatwick and Heathrow airports, Charles de Gaulle in Paris and other locations including Washington DC, Melbourne and Singapore.
Reports indicate that a computer system used by more than 100 airlines crashed, leaving passengers in some locations facing lengthy queues and delays.
According to a spokesperson at Gatwick Airport, the problem was with a computer system called Amadeus Altea which was later explained as a "network issue."
The Gatwick spokesperson denied the problem was linked specifically to the airport.
"This is an airline issue," he said, adding that there had been no major delays caused.
An Amadeus spokesperson said: "During the morning, we experienced a network issue that caused disruption to some of our systems.
"Amadeus technical teams took immediate action to identify the cause of the issue and restore services as quickly as possible.
"That action is ongoing with services gradually being restored. Amadeus regrets any inconvenience caused to customers."
A Heathrow spokesperson said: "A small number of airlines are currently experiencing intermittent issues with their check-in systems at airports around the world – including at Heathrow.
"Passengers will still be able to check-in for their flight, although the process may take slightly longer than usual. We are working closely with our airlines to help resolve the issue as quickly as possible. We apologise for any inconvenience this may cause."
Throughout the day, frustrated passengers took to social media to complain about the delays.
Skyscanner, a website dedicated to travel services, tweeted: "Check-in system failures are causing issues at six major airports around the world.
"Give yourself extra time if travelling to London Gatwick and Heathrow, Charles de Gaulle, Zurich, Melbourne, Johannesburg & Reagan Airport. Airports in Brussels, Tokyo, Hong Kong, the Netherlands & Singapore are also said to be hit with this problem too."
"This failure is affecting a lot of flights right now," it added.