Southwest Airlines temporarily grounded all US flights Tuesday due to a technology problem, delaying more than 1,700 departures and hitting its share price.
The domestic-focused US carrier "requested that the Federal Aviation Administration pause the airline's departures due to an internal technical issue at Southwest," US regulator FAA said on its Twitter feed near 1430 GMT.
But near 1510 GMT, the FAA said "the pause has been lifted their service has resumed."
In a statement after the outage ended, Southwest said the problem stemmed from "data connection issues resulting from a firewall failure," according to an email to AFP.
"Early this morning, a vendor-supplied firewall went down and connection to some operational data was unexpectedly lost. Southwest Teams worked quickly to minimize flight disruptions," the company said.
"We appreciate the patience of our customers and employees during this morning's brief disruption."
The problem has delayed 1,728 flights, according to tracking service FlightAware.
Southwest came in for heavy criticism for a major operational meltdown over the 2022-23 winter holidays when it canceled more than 16,700 flights following a bad winter storm.
The carrier has been upgrading its systems in the wake of that debacle, saying in a March 14 news release that work was underway to implement improvements.
Shares were down 0.5 percent at $32.15 after dropping nearly four percent soon after the outage was reported.