The DOT's moves come weeks after issuing a multi-million dollar fine against JetBlue.

(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.

Yesterday, the United States and U.S. Department of Transportation (DOT ... In addition, the DOT levied a fine against Frontier Airlines, which was also for chronically delayed flights.

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.

Denver-based Frontier Airlines says it’s ready to keep talking after bankrupt Spirit Airlines rejected its offer to merge.

The Transportation Department is stepping up enforcement of persistent flight delays with a lawsuit against Southwest Airlines and a fine against Frontier Airlines. The agency said the U.S ...

Secretary of Transportation Sean Duffy promised to improve the nation's transportation infrastructure and systems after Vice President JD Vance swore in Duffy on Wednesday afternoon.

The Appeals Court ruled that while the DOT had the power to issue such rules, the rulemaking process had some procedural gaps.

Spirit Airlines' executives remarked that they were still open to discussions if Frontier Airlines would improve its offer.

Frontier Airlines is attempting for a second time to merge with the now bankrupt Spirit Airlines, which declared bankruptcy late last year as budget airlines struggle.

In a presentation to Spirit dated Jan, 28, Frontier said a merger would create the nation's fifth-largest airline and "the first formidable low-cost challenger to the Big Four," referring to competitors American Airlines, United Airlines, Southwest Airlines and Delta Air Lines.