An outage at the airline reservation system Sabre caused headaches for airlines around the world early Tuesday morning.

"Sabre is experiencing a system issue," the company said in a tweet. "Our technology team is working as quickly as possible to resolve the situation."'

Virgin Australia manually checked in customers. And Johannesburg's international airport said British Airways flights experienced delays earlier.

The Sabre system is used by more than 300 airlines and more than 100 airports worldwide.