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 US Department of Transportation (USDOT) is suing Southwest Airlines for “illegally operating multiple chronically delayed flights and disrupting passengers’ travel,” according to a press release.

Having assessed a first-of-its-kind fine for “chronic flight delays” against JetBlue Airways, federal regulators have now moved to penalize both Southwest Airlines and Frontier Airlines for similar infractions.

Southwest Airlines was sued in federal court by the Department of Transportation, while Frontier was hit with a $650,000 fine.

Frontier Airlines recently announced new benefits for members of its loyalty program, including a fast-track offer that helps travelers achieve Elite Platinum status with as little as 20,000 points.

(ABC 6 News) — The U.S. Department of Transportation says it is prepared to take airlines to court over flight delays. The agency has filed a lawsuit against Southwest, accusing the airline of illegally operating chronically delayed flights and disrupting passengers’ travel plans.

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

President Joe Biden's administration on Wednesday sued Southwest Airlines , accusing the carrier of illegally operating multiple chronically delayed flights and disrupting passengers’ travel.