Computer problems have caused extensive delays and cancelations at Southwest Airlines for the second day in a row. On Monday, Southwest delayed 1,415 of its scheduled flights. On Tuesday, the airline canceled 494 flights and delayed 1,562 scheduled flights. Southwest Airlines says operations are now returning to normal.

Weather data outage causes problems on Monday

On Monday, a nationwide weather data outage at Southwest's third-party weather provider caused extensive problems across the Southwest network. The outage occurred around 21:00 local time. As a result, weather data needed to fly aircraft safely could not be transmitted. By midnight, Southwest was on top of the problem.

"While the vendor worked to restore connectivity, we implemented a ground stop to protect the safety of our crews and customers," said a statement issued by Southwest Airlines on Monday. Passengers traveling on other airlines, including Delta and Alaska, were also impacted by the outage.

Social media was flooded with tales of unhappy passengers stranded on planes and in airports while harried Southwest employees did their best to defuse tensions.

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A problem with weather data delayed Southwest flights on Monday evening. Photo: Denver International Airport

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Further computer problems for Southwest Airlines on Tuesday

In a further stroke of bad luck for Southwest Airlines, another round of IT problems crippled the airline on Tuesday afternoon. Southwest attributed this to "technical issues." However, the issues were substantial enough for the Federal Aviation Administration to issue a temporary nationwide stop at Southwest's request, grounding the airline. The FAA says a reservation computer issue was behind the request. That stop was lifted after about 45 minutes.

In another statement issued on Tuesday, Southwest Airlines said it was "in the process of investigating the root cause of each event to determine the reason behind the technology issue."

A spate of high-profile cyberattacks has recently shut down some key pieces of infrastructure across the United States. To date, airlines have proved relatively immune to this threat. On Tuesday evening, Southwest indicated it was getting on top of the computer issue.

"We are in the process of resuming normal operations after a system issue this afternoon that created flight disruptions throughout our network," the airline said on social media. "We know many Customers still require assistance and are working to address those concerns as quickly as possible."

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Airlines, including Southwest, have become more and more dependant on IT to run flight operations. Photo: Denver International Airport

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Passengers left stranded and unhappy

Southwest's call for patience from passengers caught up in the delays and cancelations left many unimpressed. Passengers on planes and left stranded in airports overnight flooded social media with complaints.

"Been a long-time customer and Southwest frequent flyer. It’s never been this bad. Been flying all day and just heard my next flight is delayed by three hours," posted one passenger.

"We have been sitting on the tarmac for two hours. We missed our connecting flight. This is the last time we fly Southwest," says another.

"Are you paying the $90 for the hotel that we booked? You canceled our flight?"

Computer problems at airlines are not new. Problems with IT systems often see airline staff having to manually check-in and board passengers. Doing so was once the norm in airports but now causes extensive delays. However, airlines have become increasingly dependant on software running normally to operate.

"Every organization is a software organization," says Jonathan Knudsen, Senior Security Strategist at Synopsys. "Every organization in every industry depends on software for critical business functions."

Early on Wednesday, Southwest already has 64 flights canceled or roughly 1% of the airline's scheduled flights. In its statement, Southwest Airlines is advising wait times on their customer care line are longer than normal and is encouraging passengers to use self-service options online.