On Wednesday, the Department of Transportation (DOT) announced that it is suing Southwest Airlines over persistent flight delays.

Transportation Secretary Pete Buttigieg issued a statement saying, “To uphold passenger rights and ensure fairness in air travel, we are taking legal action against Southwest Airlines for their continued disruption of travel due to unlawful chronic flight delays. Airlines must provide travelers with realistic departure and arrival times. Today’s action makes it clear that the Department is willing to pursue legal remedies to protect passengers.”

As per DOT records, Southwest Airlines saw two specific flights disrupted 180 times from April to August 2022. These flights were between Chicago Midway International Airport and Oakland, California, as well as between Baltimore and Cleveland.

Data from the Bureau of Transportation Statistics indicates that over 90% of the delays on these specific routes were caused directly by Southwest. The DOT noted it has guidelines giving airlines enough time to adjust schedules after chronic delays, but Southwest failed to take necessary actions to rectify the situation.

In a news release, the DOT described unrealistic scheduling as “unfair, misleading, and anti-competitive,” resulting in disruptions for travelers and allowing airlines to mislead consumers for business gain.

Marketing flights that have experienced chronic delays for four or more consecutive months qualifies as unrealistic scheduling, according to DOT regulations. A flight is categorized as chronically delayed if it operates at least ten times a month and is late by more than 30 minutes over 50% of the time, including any cancellations and diversions as delays.

The DOT plans to pursue “maximum civil penalties” in this lawsuit. The Department of Justice has claimed Southwest has violated the DOT’s unrealistic scheduling rule at least 58 times, with each violation possibly resulting in a fine of up to $37,377. This means that, based on the lawsuit’s outcome, the airline could face potential penalties around $2.2 million.

Additionally, the DOT announced enforcement actions against Frontier Airlines for chronic flight delays.

Frontier was assessed a fine of $650,000, but the airline will only need to pay $325,000 upfront. The remaining amount will be waived if Frontier does not operate any chronically delayed flights over the next three years.

Southwest Airlines expressed disappointment regarding the lawsuit in a statement, asserting, “Since the DOT released its policy on Chronically Delayed Flights (CDF) in 2009, Southwest has conducted over 20 million flights without any other CDF infractions. Any portrayal of these two flights as an unrealistic schedule is simply unfounded when compared to our track record over the past 15 years. In 2024, Southwest achieved industry-leading success by completing over 99% of its flights without cancellations.”

Frontier Airlines opted not to comment.

Earlier this month, JetBlue faced a $2 million fine from the DOT for similar issues related to chronic flight delays.

(This story has been updated to include additional information.)

Zach Wichter is a travel reporter and writes the Cruising Altitude column for YSL News. He is based in New York.