The Department of Transportation on Wednesday sued Southwest Airlines , alleging the carrier operated chronically delayed flights, and fined Frontier Airlines for late-arriving flights.
The lawsuit follows a $2 million DOT fine on JetBlue Airways for similar allegations.
The lawsuit and fines come at the end of the Biden administration, which has taken a harder line toward consumer protections than previous administrations.
The DOT said that Southwest’s flights from Chicago Midway International Airport to Oakland, California, and from Baltimore to Cleveland arrived late nearly 200 times between April and August 2022.
The DOT said each flight was chronically delayed for five consecutive months and that Southwest was responsible for more than 90% of the disruptions.
It defines a flight as chronically delayed if it is flown at least 10 times a month and arrives more than 30 minutes late more than half the time. The calculation includes cancellations and diversions.