A New York woman was sentenced to four months in federal prison after spitting on a passenger, then shoving a flight attendant on an American Airlines flight in February 2021, a year that saw a record number of incidents of unruly and violent behavior on airplanes.

Kelly Pichardo, a 32-year-old single mother who lives in the Bronx, was sentenced on Aug. 29 in U.S. District Court in Arizona, where Judge Dominic W. Lanza also ordered her to pay $9,123 in restitution. After her release from prison she will be placed on supervised release for 36 months, according to court documents.

“There is a line between boorish behavior on an airplane and criminal activity, and the defendant clearly crossed it,” Gary Restaino, the United States attorney for the district of Arizona, said in a statement.

Ms. Pichardo, who has a 12-year-old daughter and lives with her mother, did not respond to requests for comment. She pleaded guilty in May to one count of interference with a flight crew member.

“Ms. Pichardo is very ashamed of her actions on the plane that day,” her lawyer, Ana Botello, said in an email.

The altercation occurred as mask mandates and Covid-19 restrictions led to tension on airplanes, where unruly and violent passengers shoved, struck and yelled at flight attendants and other passengers.

In May 2021 a woman punched a flight attendant repeatedly, bloodying her face and chipping three of her teeth. Within days of that attack, two major airlines, American and Southwest, which had temporarily stopped serving alcohol on flights in an effort to cut down on bad behavior, postponed plans to begin serving it again. Both airlines have since resumed alcohol sales. The woman in that case was sentenced to 15 months in prison.

Ms. Pichardo was flying first class from Dallas to Los Angeles with a friend on Feb. 24, 2021, according to prosecutors and court documents that described the case.

The friend used a racial slur as they were talking, prompting a Black passenger who was sitting behind the two women to touch Ms. Pichardo on the shoulder and admonish them.

Ms. Pichardo spit on the passenger, who suffered “racist abuse,” prosecutors said.

She became “even more irate” as other passengers tried to record the interaction with their cellphone cameras, according to court documents.

A flight crew member came to defuse the situation, and Ms. Pichardo lunged at him and pushed him in the chest as she tried to move past him.

The flight was diverted to Phoenix, where Ms. Pichardo and her friend were arrested. The friend was identified by prosecutors as Leeza Rodriguez, who pleaded guilty last month to interfering with a flight attendant, according to court documents. She will be sentenced in November.

Prosecutors recommended a four-month sentence for Ms. Pichardo, arguing that it would show the public the consequences of acting “unruly on airplanes.”

“This is incredibly important now, with an uptick in these incidents over the past year,” they wrote in a sentencing memorandum, which recommends what kind of punishment a defendant should receive.

“With an increase in air travel this summer compared to years prior, there is a risk of more of these incidents occurring nationwide,” prosecutors wrote.

Reports of unruly behavior by passengers began declining soon after a federal judge in Florida struck down a federal mask mandate on public transportation in April.

Ms. Pichardo’s lawyers asked Judge Lanza to sentence her to 5 years of probation, or to let her serve her sentence at home, noting that she has been employed at a local restaurant since the time of her arrest.

They said Ms. Pichardo had been sexually abused as a child and had a history of mental illness.

“This is a case where alcohol, the stresses of flying, and the fact that Ms. Pichardo, while constricted to her airplane seat, was touched by a stranger, brought up all of the feelings she felt as an abused child and caused her to snap,” wrote Ms. Botello and another lawyer, Jon M. Sands.

It is not unusual for a defendant to get a tough sentence in a case like this, where passengers and flight crew members were attacked in a confined space, said Lisa Wayne, executive director of the National Association of Criminal Defense Lawyers. The outrage over seeing flight attendants abused has also led prosecutors and judges to seek stiff punishments against defendants accused of such crimes, she said.

“This is the worst time that you can have this kind of case,” Ms. Wayne said.

But she questioned the purpose of incarcerating Ms. Pichardo instead of letting her serve a sentence at home where she could keep working and pay the fines imposed by the court.

Sara Nelson, president of the Association of Flight Attendants-C.W.A., said sentences handed down to defendants convicted of assault should serve as a deterrent “for bad actors in the air or airports.”

“Flight attendants are aviation’s first responders, not targets for berserk passengers,” she said in a statement. “Assault is a federal crime in air travel. Period.”

A spokesman for American Airlines declined to comment on the sentence and referred to a statement the company issued shortly after Ms. Pichardo’s arrest thanking crew members “for their professionalism in managing a difficult situation.”