Frustrated Southwest pilot and union rep says the airline's flight meltdown was caused by outdated scheduling software

• Southwest Airlines has canceled nearly 2,600 flights so far on Tuesday after canceling over 2,900 on Monday.
• The carrier told Insider that "scheduling issues" can also be blamed for the mass flight disruptions.

Southwest Airlines has blamed its operational meltdown on the busy holiday weekend and the powerful winter storm but said on Tuesday its antiquated scheduling system also played a role.

On Monday, the Dallas-based carrier canceled 74% of its flights, according to FlightAware data. As of 3:30 p.m. on Tuesday, another 63% have been canceled for a total of about 2,600.

Since its original statement last updated on Tuesday, Southwest has added to its reasoning for the chaos, telling Insider, "we have had issues with our scheduling tools, causing a scheduling issue."

"We were fully staffed and prepared for the approaching holiday weekend when the severe weather swept across the continent, where Southwest is the largest carrier in 23 of the top 25 travel markets in the US," the carrier said in a statement. "These operational conditions forced daily changes to our flight schedule at a volume and magnitude that still has the tools our teams use to recover the airline operating at capacity."

Captain Mike Santoro, vice president of the Southwest Airlines Pilots Association (SWAPA), told Insider on Tuesday that while the winter storm was a "catalyst" for the disruptions, the company's "outdated" scheduling software created the snowball.

He explained the system tracks the company's pilots and flight attendants' whereabouts, but it got so overloaded that it could not keep up.

"When we get out of position, it's a tough task for our schedulers to put it back together, and right now they're having to do it by hand," he explained. "The problem is the software just doesn't keep track of us."

For example, he explained one flight had two pilots and three flight attendants assigned to a flight but needed one more flight attendant for the plane to legally fly.

There were several deadheading flight attendants onboard, meaning they were being flown to another city for an assignment but were "ready, willing, and able to work" that flight as well.

But, because the system didn't know they were on that aircraft and the flight attendants couldn't get in contact with crew scheduling, the company canceled the flight when it didn't need to.

"Even though we had a crew available, [scheduling] had no idea those flight attendants were in the back of the airplane."

Lyn Montgomery, president of Southwest's flight attendant union, TWU Local 556, also pointed to the scheduling software in an interview with Texas news outlet KHOU, saying the storm "created the issues," but the carrier failed to quickly recover to due "outdated technology."

Other airlines, like United Airlines and American Airlines, largely avoided this. This is because their systems are more modern and can handle the workload quicker than Southwest's can. The latter's systems failed to keep up because flight attendants use a system largely reliant on phone lines, Montgomery told KHOU. That system can get clogged up, forcing crews to wait on hold for hours waiting for a new assignment.

According to Southwest, to recover its operation it will "continue operating a reduced schedule by flying roughly one-third of our schedule for the next several days."

On Tuesday, Senators Edward J. Markey (D-Mass.) and Richard Blumenthal (D-Conn.), members of the Senate Commerce Committee, also pointed to "internal failures at the company," and said passengers should be compensated for the disruptions.

"Southwest cannot avoid compensating passengers by claiming these flight cancellations were caused by recent winter storms," they said. "As Southwest executives have acknowledged, the mass cancellations yesterday were largely due to the failure of its own internal systems. As such, those cancellations should be categorized as 'controllable,' and Southwest should compensate passengers accordingly."