Southwest Airlines flight cancellations and delays continued for yet another day at Chicago airports as major service disruptions that started over the weekend continued to spill into the work week.
As of Tuesday morning, 11 flight cancellations were reported for the airline at Midway Airport, with two others reported at O'Hare Airport, according to Flightaware. At Midway, 28 other Southwest flights were experiencing delays.
Just before 7 a.m., the airline had reported 87 total cancellations across airports Tuesday.
The numbers mark a continued drop from the dozens canceled over the weekend at the Chicago hubs, but the fifth straight day of cancellations.
Citing air traffic control issues and bad weather, Southwest Airlines canceled more than 1,000 flights Sunday, 27% of its schedule, including dozens set to depart from Chicago's Midway Airport.
Midway, one of the airline's major hubs, along with its other top destinations, Denver, Baltimore and Dallas Love Field, were among the hardest hit by the cancellations.
"Southwest Teams have been working diligently to restore stability to the network, and we are experiencing less disruptions on Monday," the airline said in a statement. "We hope to restore our full schedule as soon as possible."
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.
"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," the airline's statement read. "Unfortunately, the out-of-place aircraft and continued strain on our crew resources created additional cancelations across our point-to-point network that cascaded throughout the weekend and into Monday."
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 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.
Despite speculation and rumors that the flight issues may have been sparked by a work slowdown from pilots who oppose the mandate, both the airline and pilots union denied those claims.
"It's inaccurate," a Southwest spokeswoman said by email. "There's a lot of unfounded rumor and speculation circulating."
The airline later said in its statement "the operational challenges were not a result of Southwest employee demonstrations."
The pilots union also 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.