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.

Travelers can book steeply discounted flights to Mexico, the Caribbean and select U.S. destinations with one-way fares starting at just 100 miles, for a limited time only.

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."

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