American Airlines restored access to its reservation system on Tuesday afternoon after a four-hour long outage that grounded its flights across the U.S.
Problems began around 11am Central time (16:00 GMT) when the airline began suffering "intermittent outages" to its reservation system. American Airlines relies on Sabre for much of its reservations, but said the problem was with its system and not those of Sabre.
Within two hours of first notifying the public of the problems, American halted its flight operations, disrupting the travel plans of tens of thousands of travellers. The exact number of passengers affected was not immediately clear, but in March the airline carried an average of 313,000 passengers worldwide on its network per day.
At 3:30pm Central time (20:30 GMT) the problem had been fixed, the airline said.
"Our systems have been fully restored, however we expect continued flight delays and cancellations throughout the remainder of the day," the company posted on its Facebook page.
The airline is offering several options to its customers. Those at airports are being rebooked onto other flights, those that can travel on another day are being offered rebooking with no fee, and some passengers are being offered refunds.
The airline industry is hugely reliant on computers to manage the numerous passenger, baggage, scheduling and control systems that need to work in complete harmony to avoid chaos. For that reason, when a failure happens it typically affects tens of thousands of people and can have a knock-on effect for days.
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is firstname.lastname@example.org