The American Civil Liberties Union is suing the government over a February incident in which U.S. Customs and Border Protection agents asked to see identification from everyone aboard a Delta flight that had landed in New York. The agents were looking for an immigrant who had received a deportation order to leave the United States. (Mark Lennihan/Associated Press)

Nine passengers on a domestic flight for which immigration authorities made everyone show identification before they could deplane are suing the government, alleging they were subjected to an unconstitutional search, an attorney for the group said.

The passengers, represented by the American Civil Liberties Union, asked a federal judge Thursday to bar the government from requiring people to produce ID before deboarding a domestic flight without a warrant or individualized reason to do so.

ACLU Deputy Legal Director Cecillia Wang said that even though passengers are required to show identification before being allowed into the area where flights are boarded, those on board the flight were “shocked” to be asked to do so before they could leave.

“There was no lawful justification for detaining every single passenger on this domestic flight,” she said.

A Justice Department spokeswoman and a Customs and Border Protection spokesman declined to comment. The Customs and Border Protection spokesman said the lack of response “should not be construed as agreement or stipulation with any of the allegations.”

The incident occurred in February on Delta Flight 1583 from San Francisco to New York. Once on the ground at John F. Kennedy International Airport, Wang said, those on board were greeted by Customs and Border Protection agents, who stood in the boarding bridge and demanded identification documents.

Those who questioned what was happening were told it was routine, Wang said.

Kelley Amadei, 40, was flying back home to New York with her wife and 7-year-old son. As the plane was taxiing to the gate, Amadei said, a member of the flight crew announced that “nobody would be allowed to deplane until they showed government-issued identification.”

“That was alarming to me, because that’s not something I had heard before,” Amadei said.

At first, Amadei said she was scared. “My initial instinct was, ‘Has something happened? Are we in danger?’ ” But as she watched two agents block people from leaving, asking each of them for their IDs, her fear turned to outrage. She said when she approached with her son, whose skin is somewhat darker than hers, agents looked repeatedly from her to the boy.

“I said, ‘He’s seven years old, he doesn’t carry ID on him,’ ” Amadei said. Agents ultimately let her pass, and she soon contacted news outlets to share her story.

Her son, shaken by the incident, had asked if their family was in trouble.

“It felt like a violation,” Amadei said.

Authorities had been searching for an immigrant who had received a deportation order to leave the United States. The incident sparked significant controversy, as it came amid an ongoing legal fight over President Trump’s first travel ban.

The Trump administration has promised to crack down on illegal immigration and has sometimes employed controversial tactics, such as using courthouses to arrest people suspected of being in the country illegally.

An official with the Department of Homeland Security told The Washington Post after the incident that the steps Customs and Border Protection agents took were normal and did not stem from a new policy or executive order.

“When we’re asked by our law enforcement partners to assist in searching for a person of interest, we are able to, and will, help,” the official said.

The person whom agents had been seeking was not on the flight, authorities said.

Those suing include two journalists, a college professor and others, Wang said. She said they are particularly concerned with the Department of Homeland Security’s characterization of the incident as normal, because, in her view, government agents should not have been allowed to ask passengers for identification without a warrant or some suspicion of a particular person.

“We basically want to stop the government from doing this again, without any individualized suspicion,” Wang said.