A passenger who was yelling and became physically aggressive on a United Airlines flight from London to Newark in March, prompting the crew to divert the plane to Bangor, Maine, has been ordered to pay the airline $20,638 in restitution, federal prosecutors said.

The passenger, Alexander Michael Dominic MacDonald, 30, of Chelmsford, England, was also sentenced on April 25 to time already served, prosecutors said.

Mr. MacDonald had been in custody since March 1, when he was arrested after his flight landed at Bangor International Airport. He pleaded guilty on March 22 to one count of interfering with a flight crew, a felony punishable by up to 20 years in prison.

“He apologized for his actions in court and looks forward to returning home to his family in England,” Mr. MacDonald’s lawyer, Matthew D. Morgan, said in an email on Tuesday.

According to an F.B.I. affidavit, about 160 passengers and 10 crew members were aboard United Airlines Flight 883, which left Heathrow Airport near London on the morning of March 1 and was headed to Newark Liberty International Airport in New Jersey.

Several hours into the flight, the purser, or lead flight attendant, heard Mr. MacDonald “arguing loudly” with his girlfriend and asked him to lower his voice, the affidavit says. He agreed to do so, but minutes later the purser found him yelling again, this time at another flight attendant, the affidavit says.

The purser tried to calm Mr. MacDonald down but he “would not listen and continued to be verbally and physically aggressive,” according to the affidavit. Mr. MacDonald asked the purser if he wanted to “have a problem” and threatened to “mess up the plane,” the affidavit states. He also put his hands on the purser’s shoulders as he backed the purser into a corner, the document says.

With the help of another passenger, the purser restrained Mr. MacDonald in flexible handcuffs, but he “continued to be noncompliant” and the purser determined that the plane needed to land “for the safety of the crew,” the affidavit states. The captain also believed that continuing to fly to Newark “was too great a risk,” the affidavit states.

United Airlines said in a statement that the plane landed in Bangor so the “police could remove two disruptive customers who appeared to be intoxicated.” The statement did not identify those passengers but said they had both been banned from flying on United Airlines. After the passengers were removed from the plane, it continued on to Newark.

The number of incidents involving unruly passengers on airplanes has dropped steadily since it reached record highs in 2021, when passengers returning to the skies amid the easing of coronavirus restrictions reported frequent and disruptive behavior, including many heated disputes over mask rules.

In January 2021, the Federal Aviation Administration introduced a “zero-tolerance policy” regarding unruly passengers, resulting in hefty fines instead of the warning letters or counseling that were used previously. The agency said it had received 2,075 reports of unruly passengers last year, compared to 2,455 in 2022 and 5,973 in 2021.