Etihad Airways, Alaska Airlines and Virgin Australia each cited a technical problem with Sabre's airline reservation system as the cause of delays to services today.
Sabre says the system crashed for around 2h. It was restored by 06:00 UTC, the technology provider tweeted.
Abu Dhabi-based Etihad says it experienced a "reservation and check-in systems failure" which "caused some delays across the network". Alaska Airlines tweeted that the problem had forced the carrier back to "pen and paper at work". Similarly, Virgin Australia tweeted that it was manually checking in passengers, adding that flight bookings were temporarily offline, leading to delays.
"Sabre customers were unable to connect to our system for a period of time very early this morning," Sabre acknowledges. "The system was restored and all customers are able to connect to Sabre. We apologise and regret the inconvenience caused."
More than 100 airlines use Sabre's reservations system.