The Transportation Department is taking legal action against Southwest, alleging the airline illegally operated persistently delayed flights and disrupted passengers' travel plans.

On Wednesday evening, the U.S. Department of Transportation announced they will be suing Dallas-based Southwest Airlines as a way to step up enforcement of persistent flight delays. The federal agency will also put a fine against Frontier Airlines.

Co. was sued by the US Transportation Department for allegedly violating rules that require airlines to set and meet realistic flight schedules. The carrier was responsible for “unlawful chronic flight delays” that disrupted passengers’ travel plans,

The department's investigation found two Southwest Airline flights were delayed for five consecutive months in 2022. Both delayed flights resulted in more than 90% of disruptions between April and August that year.

The US Department of Transportation (DOT) has sued Southwest Airlines for allegedly operating numerous "chronically delayed" flights in violation of federal laws prohibiting deceptive practices.

DOT sues Southwest Airlines, accusing the airline of chronic flight delays while citing unrealistic scheduling that disrupted passengers.