Southwest Airlines briefly halted all of its operations on Tuesday morning, citing “intermittent technology issues.”

More than 1,249 flights, or 30% of the airline’s schedule, were delayed as of 11 a.m. ET, although that number was expected to increase throughout the day.

A ground stop order issued by the FAA was lifted shortly before 11 a.m. ET, and Southwest flights began departing airports around the U.S. shortly after.

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The airline said in a statement that an issue with a “vendor-supplied” firewall caused data connection problems within its operations teams. An internal message seen by TPG noted several computer systems that had lost connectivity.

“We ask that travelers use Southwest.com to check flight status or visit a Southwest Airlines Customer Service Agent at the airport for assistance with travel needs,” the airline said in a statement, confirming that operations had resumed. “We appreciate the patience of our Customers and Employees during this morning’s brief disruption.”

The grounding comes as Southwest continues to try and reassure customers, regulators and investors following an operational meltdown during the recent holiday travel period.

This is a developing story and will be updated. Check back for more.