The Department of Transportation alleges Southwest Airlines was “illegally operating multiple chronically delayed flights.”

Key Takeaways Southwest Airlines stock fell Thursday after the Department of Transportation sued the airline over a pair of "chronically delayed flights."The federal agency says Southwest operated two flights in 2022 that arrived later than scheduled more than half the time for five consecutive months.

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

The Department of Transportation is suing the airline for what it characterized as months of "chronically delayed" flights — those that arrive at least 30 minutes late more than half the time.