Southwest Airlines will pay a $35 million fine as part of a $140 million agreement to settle a federal investigation into a debacle in December 2022 when the airline canceled thousands of flights and stranded more than 2 million travelers over the holidays.

Most of the settlement will go toward compensating future passengers, which the U.S. Department of Transportation considers an incentive for Southwest to avoid repeating last winter’s mess.

The government said the assessment was the largest it has ever imposed on an airline for violating consumer protection laws.