Germany’s flagship airline has been fined $4 million by the U.S. Department of Transportation over allegations it discriminated against a group of Jewish passengers.

The regulator said Tuesday that Lufthansa had prohibited 128 people wearing traditional Orthodox Jewish clothing from boarding for a connecting flight in Germany as they made their way from New York City to Budapest in May 2022.

“Based on the alleged misconduct of some passengers,” DOT said, Lufthansa staff “treated them all as if they were a single group and denied them boarding,” despite many of the passengers not knowing each other nor traveling together.

Some individuals in the group allegedly violated the airline’s mask policy. Video of the incident at the time showed Lufthansa staff telling passengers that “everyone has to pay” for the mistakes of a few, then defining “everyone” as “Jewish coming from JFK.” At the time, German media reported that staff denied boarding to people they determined were Jewish because they were wearing skull caps or had sidelocks.

The penalty is the largest ever issued by the DOT against an airline for a civil rights violation.

“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,” U.S. Transportation Secretary Pete Buttigieg said in a statement.

Ambassador Deborah Lipstadt, the Biden Administration’s special envoy against antisemitism, told NBC News in 2022 that the details of how the airline had treated the passengers were “unbelievable.”

“[When] I first heard it, I said, ‘Oh, this must be wrong. Someone must be misreporting this.’ And then of course, it turned out to be precisely right — and worse than we even thought,” she said.

In a statement Tuesday, the airline said it had fully cooperated with the DOT as it conducted its investigation and that it had partnered with the American Jewish Committee in the wake of the incident. 

“Through our ongoing collaboration, we have curated a first-of-its kind training program in the airline industry for our managers and employees to address antisemitism and discrimination,” it said. “Lufthansa is dedicated to being an ambassador of goodwill, tolerance, diversity, and acceptance.”

At the time, the carrier apologized for the incident, saying it had “zero tolerance for racism, antisemitism and discrimination of any type.”

Lipstadt said in 2022: “If any airline had done it, it would have been outrageous. But the terrible, awful irony of it coming from the German national airline was outrageous.”