Southwest Airlines flights to and from San Diego International Airport were again experiencing cancellations and delays on Monday following a weekend of major service disruptions.
By midmorning Monday, the carrier had canceled about 360 flights across their network and more than 600 others were delayed, according to Flightaware.
At San Diego's airport, the majority of Southwest flight through Monday evening was delayed with a handful of cancellations. To check flight status, click here.
The Dallas-based airline had blamed air traffic control issues and weather for its weekend “operational challenges” that resulted in 1,900 canceled flights on Saturday and Sunday.
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Southwest apologized to travelers for long customer service waits and said in a statement it expected to get close to normal operations by Sunday, but disruptions worsened.
"We experienced weather challenges in our Florida airports at the beginning of the weekend, challenges that were compounded by unexpected air traffic control issues in the same region, triggering delays and prompting significant cancellations for us beginning Friday evening," a Southwest Airlines spokesperson said in a statement. "We’ve continued diligent work throughout the weekend to reset our operation with a focus on getting aircraft and crews repositioned to take care of our customers."
The Federal Aviation Administration, which provides air traffic control services, took the unusual step of pushing back against Southwest's explanation. Southwest Airlines was the only airline to report such a large percentage of canceled and delayed flights over the weekend.
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.
Last week, Southwest became the latest airline to announce it was imposing a vaccine mandate on its staff. The Dallas-based company said its workers must be fully vaccinated by Dec. 8 in order to remain at the airline. Employees can seek approval to skip the shots due to medical or religious reasons.
One analyst said a possible reason for the weekend outages may be a work slowdown by pilots who oppose the mandate. 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.
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.
Shares of Southwest Airlines Co. briefly fell more than 4% on Monday before a partial recovery; they were down 2% by midmorning.