Widespread Spirit Airlines flight cancellations this week are disrupting passengers’ travels in Atlanta and around the country.

The ultra-low-cost carrier canceled more than 370 of its flights on Tuesday, amounting to about half of its flight schedule, according to FlightAware.com. That made it the airline with the most cancellations in the country, despite its relatively small size.

At Hartsfield-Jackson International Airport, Spirit canceled more than 30 flights Tuesday, the FlightAware data show.

A Spirit spokesman said the disruptions are caused by “overlapping operational challenges including weather, system outages and staffing shortages in some areas of the operation.”

In an attempt to get its flight schedule back on track, he said the airline is making “proactive cancellations” to “reset our operations.”

Spirit is recommending passengers check their flight status before heading to the airport and use its webchat for assistance.

Not all passengers may be able to get to their destinations on Spirit.

“We’re working to provide refunds for cancellations and, when possible, to reaccommodate our Guests,” Spirit spokesman Erik Hofmeyer said in a written statement. “We sincerely regret the inconvenience this has caused.”

Spirit makes up about 3% of the traffic at Hartsfield-Jackson, but has been seeking to expand.

Airlines have been struggling to ramp up staffing to handle a rebound in air travel, with more than 2 million travelers a day passing through airport security checkpoints, according to Transportation Security Administration data.

Fort Worth, Texas-based American Airlines canceled hundreds of flights in parts of the country Tuesday as it struggles with operational disruptions after thunderstorms at its hub at Dallas Forth Worth International Airport over the weekend. But as of Tuesday afternoon, the cancellations did not include Atlanta flights.

Ultra-low-cost carriers like Spirit often operate a number of routes with fewer flights a day than large hub carriers. Airlines with multiple flights per day on a route have more leeway to rebook passengers on flights to their destinations later in the day.

The pilots union at Spirit refuted rumors of a work stoppage, posting on Twitter that it was working with others to return the airline to full operations.

The Association of Flight Attendants at Spirit issued a statement saying the cancellations and delays were due to “weather, schedule month change over, and IT outages,” and also refuted rumors of a strike. “There is no flight attendant strike,” the flight attendants union said. “Crews are not the issue.”

Atlanta-based Delta Air Lines and its partners carry more than 80% of the passengers at Hartsfield-Jackson, while Dallas-based Southwest Airlines handles nearly 9% of the passengers.

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