On Wednesday, the U.S. Department of Transportation (DOT) filed a lawsuit in a San Francisco court against Southwest Airlines over “unlawful, chronic flight delays,” U.S. Transportation Secretary Pete Buttigieg announced in a Jan. 15 statement.

Southwest Airlines is being sued and Frontier Airlines fined over chronic flight delays by the Department of Transportation, the DOT announced Wednesday. Why it matters: Wednesday's announcement by the outgoing Biden administration's Transportation Secretary,

The DOT filed a lawsuit against Southwest Airlines, citing a pattern of chronic delays, as the government pushes for stricter accountability.

The lawsuit alleges Southwest illegally operated chronically delayed flights and disrupted passengers' travel plans.

A lawsuit filed against Southwest alleges the airline operated multiple “chronically delayed” flights affecting thousands of passengers.

Southwest is disappointed that DOT chose to file a lawsuit over two flights that occurred more than two years ago," a spokesperson for the airline said.

The Department of Transportation is suing Southwest Airlines, accusing it of operating two “chronically delayed flights” in 2022 that resulted in 180 flight disruptions.

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 Department of Transportation found that Southwest was responsible for 90% of the disruptions on two flights.

The Department of Transportation said that two Southwest Airlines routes arrived late nearly 180 times in a five-month period in 2022.

The agency is seeking civil penalties against Southwest Airlines, and also fined Frontier Airlines for its continuous delays.

Transportation Secretary Pete Buttigieg said airlines have a legal obligation to ensure that their schedules list realistic departure and arrival times.