Southwest Airlines has resumed all U.S. operations following a temporary grounding of all planes as the airline worked to resolves a "firewall failure," a spokesperson told Semafor.
"Southwest has resumed operations after temporarily pausing flight activity this morning to work through data connection issues resulting from a firewall failure," the spokesperson said. "Early this morning, a vendor-supplied firewall went down and connection to some operational data was unexpectedly lost."
The FAA's command center on Tuesday showed the agency had initiated a shutdown due to "equipment issues." The notice appears to have affected at least 800 planes.
The FAA did not immediately respond to Semafor's request for comment.
Affected passengers began voicing their frustrations on social media.
"Once again sitting on a flight and being delayed," tweeted one user. "What is wrong with your leadership?? Isn’t time for a change and a new CEO."
The Southwest Airlines Pilot's Association appeared to mock the company's issues on Twitter.
"The @SouthwestAir triple crown today?: We have the Most cancellations, Most DOT complaints, Most Major contracts past amenable date…THE NEW TRIPLE CROWN!!"
Southwest Airlines — the world's largest budget airline — was heavily criticized this past holiday season for using old booking and flight management software that was unable to keep up with the location of aircraft and crew following last year's winter storm.
While other airlines recovered to about 4% cancellations of scheduled flights after the storm, Southwest's cancellation rate remained well above 60% for days, stranding thousands of passengers, many of whom were unable to access their luggage.