"We understand several airlines are experiencing technical difficulties; we can confirm this is not a Sabre software issue", Sabre told Newsweek on Monday. The delays appeared to take place all over the country.
The airlines had halted flights after experiencing a technical problem with the "aircraft weight and balance data", according to news reports. Mainline and regional carriers were affected to varying degrees. Here, passengers wait to board a delayed Southwest flight at Ronald Reagan Washington National Airport in Arlington, Va.
According to Flight Aware, there were 21 Southwest cancellations nationwide as of 6:10 a.m. and more than 160 delays.
Computer outages Monday morning were causing flights to be delayed out of several airports across the country. The airline anticipates scattered delays. Delta said it didn't expect any cancellations among the Delta Express flights delayed by the outage.
FlightAware, an airline tracking website, said Southwest had delayed 775 flights, or 18 percent of its USA flights on Monday.
Other airlines also reported a series of delays as a result of the problem. For affected airlines, the early disruption sent ripples through their flights Monday morning.
According to posts from airline social media accounts, the issues impacted flights system-wide.
Southwest said it lifted an internal ground stop at 7.05am ET, after about 40 minutes.
Kate Modolo of Delta said that the outage prevented some of its Delta Connection flights from leaving on time.