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Southwest Airlines canceled more than 2,000 flights this past weekend due to multiple issues, leaving passengers stranded across the US. But don’t blame the mass cancellations on protests against a COVID-19 vaccine mandate. 

Some people on social media had speculated that the widespread disruption was due to pilots or air traffic controllers protesting . The Federal Aviation Administration and the airline say this isn’t true. 

What caused all the flight cancellations?

this past weekend were canceled. The airline cited issues of weather and limited staffing at Florida airports. “ATC issues and disruptive weather have resulted in a high volume of cancellations throughout the weekend while we work to recover our operation,” Southwest said in a .

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The airline added more details about the issues on Monday.

“On Friday evening, the airline ended the day with numerous cancellations, primarily created by weather and other external constraints, which left aircraft and crews out of pre-planned positions to operate our schedule on Saturday,” . “Unfortunately, the out-of-place aircraft and continued strain on our crew resources created additional cancellations across our point-to-point network that cascaded throughout the weekend and into Monday.”

The FAA confirmed that weather and staff shortage issues as well as military training Friday near the Jacksonville Air Route Traffic Control Center in Hilliard, Florida, contributed to the cancellations. 

This created a cascading effect for Southwest that continued into Monday, with more than 300 flights canceled, according to . 

Are the cancellations due to walkouts over COVID-19 vaccine mandates?

No, according to Southwest and the FAA. 

A began circulating Saturday alleging a walkout of air traffic controllers at the Jacksonville International Airport due to a . Others on social media suggested Southwest employees are protesting the . 

and , both Republicans from Texas, tweeted about the cancellations. Roy said while he was unsure if this was airline employees or air traffic controllers rebelling, they would have his support. Cruz put the blame on Biden’s push for vaccine mandates. 

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In regard to the rumor of an air traffic controller walkout, flights in and out of the Jacksonville International Airport — where many Southwest flights were canceled — are handled by the Jacksonville Air Route Traffic Control Center. The FAA, which employees most air traffic controllers, said in a statement Monday there have been no staff shortages since Friday.

In a letter to the Jacksonville Aviation Authority board of directors received by on Sunday, Jacksonville Aviation Authority COO Tony Cugno said the air traffic controller staff issue at the Jacksonville Air Route Traffic Control Center was a combination of different factors. The first was approved leave for employees, and the second was a required 48-hour period when employees at the center have to stay home to self-monitor for any side effects after receiving a vaccine shot.

The FAA said it’s working to have its workers . 

Another issue with the rumor: There would have been far more cancellations by other airlines if there was a walkout by air traffic controllers. According to FlightAware, , while the US airline with the second-most cancellations was . 

On Oct. 4, Southwest said it will require . However, it confirmed in an emailed statement that the weekend’s canceled flights weren’t due to their new requirements.  

“There is no truth behind the rumors that this is a job-related action,” the company said.

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The Southwest Airlines Pilots Association (SWAPA) that represents the airlines’ pilots also confirmed the cancellations weren’t due to a protest over the company’s vaccination requirements, according to a report from the . 

The COVID  in preventing hospitalization. Over the summer, as the delta variant swept across the US, the number of COVID-19 cases, hospitalizations and deaths surged. As some states see record numbers of cases, unvaccinated people have accounted for nearly all the hospitalizations and deaths — . With the federal mandates, the Biden administration aims to counter the surge and put pressure on the tens of millions of people who are eligible but aren’t yet vaccinated.

Why did this only affect Southwest? 

This past weekend exposed some issues with Southwest’s business strategy. Though it’s one of the , it’s feeling the effects of the COVID pandemic. 

“We were thinly staffed coming into the weekend,” Southwest Airlines CEO Gary Kelly CNBC on Tuesday. “We were significantly set behind on Friday, and it takes several days to catch up.” 

It also doesn’t help that Southwest uses a linear route network, also called . With this model, airplanes go directly from one city to another without going through a major hub city, like Delta Airlines flights do with, for instance, Hartsfield-Jackson International Airport in Atlanta and United Airlines flights do with, for example, Chicago O’Hare airport. One of the benefits of Southwest’s strategy is that it lets the airline deal with airports that have less traffic, which keeps costs down and lets the company pass the savings on to customers as lower ticket prices. On the other hand, a major issue can cause a domino effect. 

In the case of this past weekend, there were thunderstorms across Florida on Friday, which caused the initial disruption. “Every single airport in the state of Florida was impacted by this,” Kelly said. “We’re probably the largest airlines in terms of seats offered in the state of Florida.”

The combination of those delays and cancellations due to weather in Florida created a ripple effect as other factors came into play. For instance, the FAA requires flight crews to take an . When a flight is delayed by several hours on a Friday, and that same crew is supposed to be handling a flight Saturday morning, they’re required to wait those eight hours before they can work on that next flight. This pushes back that flight. Because of Southwest’s point-to-point model, the plane that was going to travel to four or five cities that day won’t make those flights, and there isn’t a hub for those passengers to get rerouted. 

Southwest employees have complained for months about their exhaustion. Unions for Southwest said in August that  the company had scheduled. 

Southwest also . If a Delta flight is canceled, Delta can offer passengers a flight on American. 

Southwest’s weekend fiasco was a headache for many travelers, but the cause wasn’t an employee uprising over vaccine mandates. The airline has urged people impacted by delayed and SCR888 canceled flights to on Southwest.com.