CNN
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Hundreds of Southwest Airlines flights were delayed after technical issues that prompted the airline to temporarily halt its operations on Tuesday morning.

Southwest said the flight delays were the result of “data connection issues resulting from a firewall failure,” a problem that led to a brief ground stop.

The Federal Aviation Administration initiated the ground stop at the airline’s request, citing “equipment issues.” The ground stop was soon lifted, and in a tweet at 11:35 a.m. ET Southwest said it had resumed operations.

“Early this morning, a vendor-supplied firewall went down and connection to some operational data was unexpectedly lost,” spokesman Dan Landson said in a statement.

Southwest had delayed 1,820 flights or 43% of its schedule as of just after noon Tuesday, according to FlightAware. The airline has canceled only nine flights on Tuesday, according to FlightAware. Southwest says its workers “worked quickly to minimize disruptions.”

Southwest reported technology issues Tuesday morning and said it would “hopefully be resuming our operation as soon as possible.”

The FAA in a statement told CNN that Southwest “requested the FAA pause the airline’s departures.”

The problems come months after the airline was forced to cancel more than 16,700 flights between December 20 and 29, roughly half its schedule during that period. The airline attributed the meltdown in part to changes to its staff scheduling computer systems. Southwest last month unveiled an “action plan” to prevent another operational meltdown.

Southwest called the latest problem “intermittent technology issues” in a social media post to customers. Several took to social media to complain about delayed flights.

“We apologize for any inconvenience this may cause, but we’re hoping to get everyone going ASAP,” the airline wrote in another social media post.

A massive winter storm started the service problems during the holiday season, but Southwest had a much tougher time recovering because of an antiquated crew scheduling system that was quickly overwhelmed, leaving the airline unable to get the staffing it needed to locations to operate flights. Nearly half of its schedule was canceled during from December 20 to December 29. Some days, as many as 75% of its scheduled flights were grounded.

Part of what created worse problems at Southwest than at other airlines is that crew members had to call in to the airline, rather than notify it electronically, to let them it of their availability.