Here’s an indisputable truth about flying: It’s impossible to escape boorish behavior when you’re 30,000 feet in the air and your plane isn’t landing for several hours.

And there is no shortage of temper-igniting types who seem to revel in rudeness upon boarding a plane. How about the guy who takes the seat next to you and unwraps a tuna and onion sandwich that immediately makes the cabin smell like a wharf?

An obnoxious drunk, a flu-ridden person sniffling and sneezing into their hand, or someone whose relationship with deodorant is on the skids – all of them prove that in-flight offensiveness knows no bounds.

“When you travel, you shouldn’t leave your manners at home,” said Jacqueline Whitmore, an international etiquette expert and founder of the Protocol School of Palm Beach. “But I think rudeness has become more prevalent in flying, probably because air travel has become more stressful than ever and so many things can trigger inappropriate behavior.”

Whitmore, a former flight attendant, can quickly rattle off a litany of the most objectionable activities she has witnessed both on the job and as a passenger.

“I have seen and heard people clip their fingernails. I have seen people take off their shoes and expose their smelly feet,” she said. “I’ve seen people put their feet on the back of the seat in front of them. I’ve seen people put dirty baby diapers on the beverage cart.”

Diane Gottsman, author of “Modern Etiquette for a Better Life,” and founder of the Protocol School of Texas, said people often aren’t on their best behavior when using overhead bins.

“If you’re moving everyone’s luggage around while trying to cram your own into the bin, you’re probably not thinking that some other person’s bag might be full of fragile souvenirs,” she said. “You’re probably not concerned you could break something.”

Being overly friendly on a flight isn’t inherently impolite. Still, Whitmore cautioned not to forget the essential item that can help when the stranger sitting next to you wants to treat you to their life story for the entire flight.

“I’ve always said that whether you plan to use them or not, don’t leave home without your earbuds,” she said. “If you’re sitting next to a compulsive talker, your earbuds can be like putting a ‘Do Not Disturb” sign on yourself.”

Airline passengers aren’t shy about sharing what they consider to be the rudest behaviors while flying. Expedia releases an airplane etiquette study annually, and people surveyed for the 2019 edition told the travel website that the five most annoying types of passengers are:

• The germ spreader (achoo!)
• The seat kicker-bumper-grabber
• The drunk passenger
• The ‘aromatic’ passenger
• The inattentive parent

How best to deal with confronting the inevitable impolite behavior that occurs when flying? Daniel Post Senning, the great-great grandson of etiquette pioneer Emily Post and spokesman for the Emily Post Institute, offered a suggestion.

“The vast majority of rude behavior is unintentional,” he said. “You perhaps can feel less aggrieved by reminding yourself that the passenger who is being annoying or irritating probably doesn’t realize they are doing so.”

Regarding the oft-contested territory of armrests, Gottsman said that the unwritten rule is that the person in the middle seat gets the two on either side of them because that person is the one most inconvenienced by the seating arrangement.

“But that’s not tried-and-true gospel,” she said. “If someone has their arm on one of the armrests that the middle seat passenger traditionally gets, people shouldn’t start a war over it.”

Senning also suggested mentally and emotionally preparing yourself before a flight, understanding the situation will be fluid and likely come with challenges that could include rude behavior.

“Then when you’re on the plane, take a deep breath, smile and practice empathy,” he said. “Realize that the person with the screaming baby next to you didn’t intend for that to happen and probably feels worse about it than you do. By practicing empathy, all of a sudden you’re not frustrated or at least less frustrated.”