Southwest Airlines said flight delays Tuesday morning 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 lifted the ground stop for Southwest Airlines flights after earlier issuing the order, citing "equipment issues." In a tweet at 11:35 a.m. 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 has delayed 1,728 flights or 41% of its schedule as late Tuesday morning, according to FlightAware. The airline has canceled only nine flights on Tuesday, according to FlightAware. Southwest says its workers "worked quickly to minimize disruptions" and that it has resumed operations.
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There was a hold on flights into Dallas Love Field Airport, the FAA says. There still may be other residual flight delays as a result of the pause.
"Southwest Airlines requested the FAA pause the airline's departures," the agency told CNN in a statement.
Southwest reported technology issues Tuesday morning and said it would "hopefully be resuming our operation as soon as possible."
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 problem "intermittent technology issues" in a social media post to customers. Several have taken 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.
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