WASHINGTON — Attorney General Merrick Garland directed US attorneys across the country to swiftly prioritize prosecution of federal crimes that happen on commercial flights as federal officials face a historic number of investigations into passenger behavior.

Garland’s memo, issued Wednesday, emphasizes that the Justice Department is committed to aggressively prosecuting violent passengers who assault crew members or endanger the safety of other passengers. Federal law prohibits interfering with a flight crew, including assaulting, intimidating or threatening crew members.

In a statement, Garland said such passengers do more than harm employees. “They prevent the performance of critical duties that help ensure safe air travel. Similarly, when passengers commit violent acts against other passengers in the close confines of a commercial aircraft, the conduct endangers everyone aboard,” he said.

The memo also notes that dozens of incidents have been reported to the FBI by the Federal Aviation Administration — it investigates some flight disturbances and can issue civil fines to disruptive passengers — as part of an “information-sharing protocol” between the two agencies.

The FAA said earlier this month that it had launched 950 investigations into passenger behavior on flights this year. That is the highest total since the agency started keeping track in 1995. In the five years from 2016 through 2020, the agency averaged 136 investigations a year.

The agency also said that it had referred 37 cases involving unruly airline passengers to the FBI for possible criminal prosecution since the number of disruptions on flights began to spike in January.

“The unacceptable disruptive behavior that we’re seeing is a serious safety threat to flights, and we’re committed to our partnership with the DOJ to combat it,” FAA Administrator Steve Dickson said.

Airlines and their unions have pressed the federal government to push more aggressively for criminal prosecution. Airlines have reported more than 5,000 incidents involving unruly passengers this year, with more than 3,600 of those involving people who refused to wear face masks as required by federal regulation.

“The Department of Justice is committed to using its resources to do its part to prevent violence, intimidation, threats of violence and other criminal behavior that endangers the safety of passengers, flight crews and flight attendants on commercial aircraft,” Garland said in the statement.

The international president of the Association of Flight Attendants-CWA, AFL-CIO, Sara Nelson, also applauded Garland’s announcement.

“Consequences need to be swift and clear to keep travel safe and protect the people on the frontlines who have worked through all the stresses of this pandemic,” Nelson said in a statement. “We want to take people to New Orleans, Seattle, Fort Lauderdale, or to see Grandma. We do not want to take them to jail. But, the DOJ can now make it clear that’s where you’re going if you refuse to cooperate and act out violently on a plane.”