The U.S. Department of Transportation (DOT) has accused Lufthansa of discriminating against over 100 Jewish passengers back in 2022 and fined the German airline $4 million – the largest such fine the department has ever issued, it said on Tuesday.

The fine is based on a civil rights complaint filed by the DOT against Lufthansa.

The case stems from a flight from Frankfurt to Budapest in May 2022, in which 128 passengers from New York, most of whom were wearing clothing typical of Orthodox Jewish men, were banned from boarding their connecting flight in Germany due to the "alleged misconduct" of a few passengers.

On the flight from New York to Frankfurt, orders to wear face masks and not congregate in the aisles were reportedly not adhered to by some of the 128 passengers, though the airline did not identify particular passengers, the DOT's consent decree said.

"Despite many of the passengers not knowing each other nor traveling together, passengers interviewed by DOT investigators stated that Lufthansa treated them all as if they were a single group and denied them boarding for the alleged misbehavior of a few," the DOT said in a statement.

Lufthansa "denies any suggestion that any of its employees engaged in any form of discrimination," according to the DOT's consent decree. The company regrets the circumstances that led to the decision to deny the passengers boarding and has apologized publicly on numerous occasions, DOT said in its statement.

"Lufthansa notes that the denied boarding incident at FRA (the Frankfurt Airport) resulted from an unfortunate series of inaccurate communications, misinterpretations and misjudgments throughout the decision-making process," the order stated.

"No one should face discrimination when they travel, and today’s action sends a clear message to the airline industry that we are prepared to investigate and take action whenever passengers’ civil rights are violated," said U.S. Transportation Secretary Pete Buttigieg in the DOT statement.