The Transportation Department on Monday announced a $140 million fine against Southwest Airlines for a crisis last winter that disrupted travel for about two million people during the holiday season.

Of the $140 million, Southwest Airlines will pay $35 million to the federal government. For the remaining amount, the department is crediting the airline for providing frequent flyer points as an apology to customers affected by the crisis, and for agreeing to provide tens of millions of dollars in vouchers to customers affected by future delays and cancellations.

The fine is about 30 times larger than what had previously been the department’s largest penalty against an airline for consumer protection violations, a $4.5 million deal with Air Canada in 2021 regarding customer refunds.

“Today’s action sets a new precedent and sends a clear message: If airlines fail their passengers, we will use all of our authority to hold them accountable,” Transportation Secretary Pete Buttigieg said in a statement. “Taking care of passengers is not just the right thing to do: it is necessary, and this sanction should alert all airlines to take all possible measures to ensure that a collapse like this never happens again.”

The department said Southwest had violated consumer protection laws by failing to provide prompt customer service, flight notifications and refunds to passengers affected by the crisis. In a statement, Bob Jordan, Southwest’s chief executive, said the airline had been working since last winter to improve its service.

“We spent the last year highly focused on efforts to improve the customer experience with significant investments and initiatives that accelerate operational resiliency, improve cross-team collaboration, and bolster overall readiness for winter operations,” Jordan said.

As part of Monday’s announcement, the Transportation Department said it would require Southwest to provide at least $90 million in vouchers to customers who experience severe disruptions caused by the airline in the future. Under that policy, which the airline plans to implement in May, passengers will be able to request a voucher of $75 or more if they arrive at their final destination at least three hours late due to factors within Southwest’s control. This bonus would be added to the compensation provided for hotels and food.

The fine against Southwest comes nearly a year after the holiday crisis, which began when the airline struggled to overcome severe weather. In the end, Southwest canceled nearly 17,000 flights. Many travelers were forced to make expensive and burdensome last-minute plans, with some spending hundreds of dollars or traveling long distances to reach their destinations. Southwest customers also reported being on hold for hours to speak with the airline’s customer service representatives.

The crisis cost Southwest about $1.2 billion, mostly in lost business and refunds. For weeks, the airline was the butt of late-night jokes and the subject of widespread criticism, culminating in a Senate hearing in February in which lawmakers grilled the company’s chief operating officer.

Southwest has identified three root causes of the collapse: the airline was unprepared for severe weather conditions, lacked the ability to reorganize planes and crews as quickly as necessary, and had communication gaps between teams. To address those issues, the airline has invested in equipment and infrastructure to improve its response to cold winter weather. It has made organizational changes to better monitor and respond to disruptions, and has accelerated investments in its operations, including improving crew notification and scheduling systems.

So far, Southwest has successfully avoided a repeat of last year’s debacle. Through the first nine months of this year, it has performed in line with the rest of the industry, with about 75 percent of its roughly one million flights arriving at their destination within 15 minutes of their scheduled arrival time. according to federal data. Southwest also canceled slightly fewer flights than the industry average.

Despite incurring a small loss earlier in the year, Southwest made a profit of $717 million through the first nine months of 2023. In a regulatory filing last week, the airline said it had made record revenue over the holiday. Thanksgiving and that short-term ticket sales had performed better than expected in recent weeks.

As part of its announcement Monday, the Transportation Department also said it was closing an investigation into whether Southwest had offered an unrealistic flight schedule during the holidays last year, which the department considers an unfair and deceptive practice. The department said it would close the investigation without reaching a finding on the matter, but would continue to monitor the practice across the industry.