Aeroplanes, with their cramped quarters and crowded conditions, would seem improbable settings for sexual assaults, but recent news accounts show they do happen.

A Detroit-area man who was convicted of sexually assaulting a sleeping passenger during an overnight flight was sentenced to nine years in prison. Two men were charged in separate cases in 2018. In August, a female passenger described on Twitter how a man masturbated sitting next to her for hours.

And on 18 March, two flight attendants for JetBlue filed a lawsuit in a federal court against the airline and two of its pilots, alleging that the pilots drugged both attendants during a layover and that one of the pilots raped one of the women and a co-worker.

Laura Palumbo, communications director at the National Sexual Violence Resource Center in Harrisburg, Pennsylvania, said there was every reason to believe that sexual assaults and harassment on flights had started getting increased attention thanks to the #MeToo movement and after a 2016 report that Donald Trump, decades before he became president, sexually assaulted a businesswoman on a flight. (He denied the allegation.)

Reports are poorly tracked

Definitive figures about sexual assaults on flights are elusive because no clearinghouse for data exists, the figures that are collected are scattershot and sexual assaults are the most underreported of violent crimes, experts said.

The FBI tracks only the cases that are reported to it, and the federal Department of Transportation said it forwards such reports to the relevant airline, not to other federal authorities.

Ayn Dietrich-Williams, a spokeswoman for the FBI’s Seattle field office, which started an awareness campaign about in-flight sexual assaults, said the number of such assaults reported to the bureau climbed to 63 in the 2017 fiscal year from 38 in the 2014 fiscal year. It dropped to 39 in the 2018 fiscal year.

One-fifth of flight attendants said they had received a report of passenger-on-passenger sexual assault while working on a flight, according to a 2017 survey by the Association of Flight Attendants-CWA. Law enforcement officials were contacted or met the plane less than half the time, the survey found.

Every woman to make sexual assault claims against Donald Trump Show all 16 1 /16 Every woman to make sexual assault claims against Donald Trump Every woman to make sexual assault claims against Donald Trump E Jean Carroll Author Carroll alleges that Trump pinned her against a wall and forced himself upon her in the changing rooms of a Manhattan department store in the mid-90s Getty Every woman to make sexual assault claims against Donald Trump Kristin Anderson Anderson alleges that Mr Trump touched her genitals while at a club in the early 1990s Every woman to make sexual assault claims against Donald Trump Jessica Leeds Leeds told the New York Times that Mr Trump groped her on an airplane in the 1980s BBC Every woman to make sexual assault claims against Donald Trump Natasha Stoynoff Stoynoff alleged that Mr Trump forcefully kissed her before an interview at his Mar-A-Lago estate in 2005 Everipedia Every woman to make sexual assault claims against Donald Trump Karena Virginia Virginia alleges Mr Trump groped her in 1998 outside of the US Open tennis tournament BBC News Every woman to make sexual assault claims against Donald Trump Temple Taggart Taggart claims Mr Trump gave her a kiss without consent during a rehearsal for a 1997 Miss USA pageant Every woman to make sexual assault claims against Donald Trump Summer Zervos The former Apprentice contestant alleged that Mr Trump kissed and groped her at a Beverly Hills hotel in 2007 Every woman to make sexual assault claims against Donald Trump Alva Johnson A former staffer for Trump's campaign, Johnson alleges that Trump forcibly tried to kiss her after a rally in August 2016 MSNBC Every woman to make sexual assault claims against Donald Trump Jennifer Murphy The former Apprentice contestant said Mr Trump "surprise kissed" her - but she said it did not bother her Every woman to make sexual assault claims against Donald Trump Jill Harth The makeup artist accused Mr Trump of "attempted rape" while in his daughter's room in 1997 Every woman to make sexual assault claims against Donald Trump Mindy McGillivray McGillivray alleges Mr Trump groped her at Mar-A-Lago in 2013 AP Every woman to make sexual assault claims against Donald Trump Rachel Crooks Crooks says that kissed her on the cheeks and mouth when she introduced herself to him in 2005 Every woman to make sexual assault claims against Donald Trump Mindy McGillivray McGillivray claims that Trump grabbed her backside at Mar-a-Lago in 2006 CNN Every woman to make sexual assault claims against Donald Trump Cassandra Searles The former Miss Washington alleges that Trump repeatedly grabbed her backside and invited her to his hotel room Getty Every woman to make sexual assault claims against Donald Trump Jessica Drake Drake claims that when she and two other women arrived to Trump's hotel room at his invitation, he arrived at the door in pyjamas and tightly hugged and kissed each of the woman without permission Getty Every woman to make sexual assault claims against Donald Trump Ninni Laaksonen The former Miss Finland claims that Trump squeezed her behind before they appeared together on the Late Show with David Letterman in 2006 EPA

The International Air Transport Association, an industry trade group, collects figures about disruptive passengers, a label that covers an array of behaviour, including physical touching and racial slurs.

However, not every airline is an association member, not every member submits data and the filings are voluntary, making it “likely that the statistics significantly underestimate” the reports, the association said.

Investigations can also be a jurisdictional maze, depending on which agency an assault is reported to, Ms Palumbo said. It is not unusual for victims to return home and file a report with their local police department, which might then say it does not have the authority to follow up.

“For victims and survivors, every barrier to making this report increases the likelihood that they just will give up and not report,” she said.

Predators ignore fears of getting caught

Considering the crowded, confined space on a plane, wouldn’t an assailant fear being caught?

Kris Macomber, an assistant professor of sociology at Meredith College in Raleigh, North Carolina, said the attacks were an extension of what women have long endured in other public spaces, such as streets, buses and subways.

Any fear predators might have about getting caught is overcome by their perceived sense of control.

Sharm el Sheikh: Why is there a ban on British flights to the Egyptian resort?

We also live in an “era of distraction” in which passengers watch movies, listen to music or take sleep medications, making intervention by fellow passengers less likely, Ms Macomber said.

Ms Palumbo said attacks had been known to happen in broad daylight and to passengers in aisle seats where they would be visible to even more potential witnesses.

Authorities offer safety advice

The FBI said offenders would test victims’ boundaries by pretending to brush against them to see if they react or wake up. The agency suggested keeping the armrest down between you and your seat mates no matter how friendly they might appear.

Tammy Yard-McCracken, owner of Personal Defense Industries in Virginia and a certified conflict communication instructor, recommended that passengers be mindful about what they divulge to strangers.

“Everything you say is information,” she said. “People don’t think about what they say in casual social settings.”

She recalled overhearing a woman tell a seat-mate that the previous six months had been tough because of a divorce. “That’s intel to somebody who is target hunting,” she said.

If you want to politely end a conversation with a stranger, say you need to catch up on reading or work and take out a book or a laptop.

You could also put in earbuds, which Ms Yard-McCracken described as “the universal signal that I’m not talking to other people.”

If you are trying to ditch someone who you no longer want to talk to and signal you are going to end the chat, put in the buds and leave the music off.

Be prepared to escalate your responses

If a person makes you uncomfortable or is invading your personal space, ask to be relocated, Ms Palumbo said. Don’t hesitate to press the call button for a flight attendant or leave your seat to seek one.

Ms Yard-McCracken recommended responding to transgressions of social norms by setting boundaries.

Ask the person to stop the intrusive behaviour: “Can you please stop touching my leg?” If it persists, escalate to a “command statement,” such as, “I need you to stop touching my leg.”

Failing that, use a “statement of consequences,” such as, “If you don’t stop touching my leg, I will call a flight attendant.”

Rory Miller, a former corrections officer who has written books about self-defence, suggested calling attention to yourself.

“If you just say it loudly enough that everyone looks at you, ‘Hey you pervert, keep your hands off me,'” he said, “everyone looks and keeps on looking. ‘Pervert’ is a magic word for self-defence.”

The industry and regulators are taking steps

A Federal Aviation Administration reauthorisation bill last year included the creation of a sexual misconduct task force.

The flight attendants’ union has spearheaded action on the issue. The union’s international president, Sara Nelson, said executives from airlines such as Alaska, United and Spirit had made it clear they have zero tolerance for sexual harassment of their staff or passengers.

Slavery victim trafficked to UK aged three and subject to decades of sexual abuse told to ‘go home’

She said a cultural change was needed at every level — from flight crews to air traffic controllers and airport personnel — that sexual harassment and assaults will be taken seriously.

“Ultimately, this is not going to get resolved by putting this on the victim to solve it,” Ms Nelson said. “It really does take everyone speaking up and saying this has got to be different.”