DALLAS (CBSDFW.COM/AP) — Southwest Airlines is canceling flights again today after mass cancellations over the weekend.

Frustration is running high at Dallas Love Field and across the country as some 365 flights — 10% of the airline’s schedule for the day — were canceled by late Monday morning, leaving thousands of people stranded across the country. More than 600 other flights were listed as ‘delayed’.

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Traveler Levi Stinson said, “We couldn’t even sleep last night really, just because we didn’t know what was going to happen.”

Stinson’s story isn’t unique as thousands of Southwest Airlines passengers were left stranded because their flights were canceled or delayed.

On Saturday more than 800 flights were canceled — on Sunday it was over 1,000.

Southwest blamed air traffic control problems and disruptive weather along with staffing issues in Florida.

But some customers aren’t buying it. “There’s no explanation for this problem, so I suspect that Southwest isn’t being totally honest with us,” said passenger Jeff Coles, whose flight was canceled.

Affected travelers are being advised to check their flight status and explore self-service rebooking options online.

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The widespread disruptions began shortly after the union for its pilots asked a federal court to block the airline’s order that all employees get vaccinated against COVID-19. The union said it doesn’t oppose vaccination, but it argued in a filing Friday that Southwest must negotiate before taking such a step.

As the scope of Southwest’s operational meltdown became clear over the weekend, the pilots’ union denied reports that pilots were conducting a sickout or slowdown to protest the vaccine mandate. The Southwest Airlines Pilots Association said it “has not authorized, and will not condone, any job action.”

The union offered another explanation: It said Southwest’s operation “has become brittle and subject to massive failures under the slightest pressure” because of a lack of support from the company. The union complained about the “already strained relationship” between it and the company.

The White House has pushed airlines to adopt vaccine mandates because they get paid under federal contracts, making them subject to President Joe Biden’s order that federal contractors require vaccination among employees.

United Airlines was the first major U.S. carrier to announce a vaccination requirement. Southwest had remained silent even after Biden announced his order for federal contractors and large employers. Finally last week Southwest told employees they must be fully vaccinated by Dec. 8 to keep their jobs. Workers can ask to skip the shots for medical or religious reasons.

Savanthi Syth, an airlines analyst for Raymond James, said the weekend problems will increase Southwest’ costs and worsen the company’s strained relations with unions.

Southwest has struggled all summer with high numbers of delayed and canceled flights. In August it announced it was trimming its September schedule by 27 flights a day, or less than 1%, and 162 flights a day, or 4.5% of the schedule, from early October through Nov. 5.

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CBSDFW.com Staff