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

The Department of Transportation on Wednesday sued Southwest Airlines, alleging the carrier operated chronically delayed flights, and fined Frontier Airlines for late-arriving flights.

The department said Southwest operated two chronically delayed flights – one between Chicago and Oakland, California, and another between Baltimore and Cleveland for five months in 2022. The department also said on Wednesday that it was fining Frontier Airlines $650,

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