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

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

This "sends a message to all airlines" that DOT will go to court in order "to enforce passenger protections," Pete Buttigieg said.

The United States government is suing Southwest and Frontier Airlines, alleging "chronically delayed flights."

Frontier Airlines has launched a new promotion where they will be giving away one year’s worth of free flights. Their “New Year, New Adventure” promotion will see one lucky person selected to receive free flights all year with the ability to choose from a range of international and domestic routes.

The lawsuit filed in California alleges that Southwest illegally operated chronically delayed flights and disrupted passengers’ travel plans.