British Airways has canceled nearly 100 flights from the UK's two busiest airports after experiencing IT problems with the check-in system.
Thousands of passengers were affected after the airline dropped 81 flights as a result of operations to or from Heathrow and 10 at Gatwick, while we delayed more than 200 other flights on Wednesday.
Images showed long queues of passengers at London airports and error messages on the BA app as some services hung more than five hours behind schedule.
The airline uses backup systems and manual systems to try to cope with the problems.
A spokesperson said: "We apologize to our customers for disrupting their travel plans.
" We are working as quickly as possible to resolve a system issue that has resulted in a number of cancellations and delays today.
"A number of flights continue to operate, but we advise customers to check ba.com for the latest flight information before arriving at the airport."
The airline offers short-haul passengers departing from Heathrow, Gatwick and London City the chance to book for another day between Thursday and next Tuesday.
On Wednesday, holidaymakers had a struggle to get to Gatwick after the Gatwick Express train service from London Victoria was canceled.
A fire on the tracks between Victoria and Clapham Junction got all southern and Gatwick Express trains canceled early.