If you clench your fists and gnash your teeth at the very thought of paying anything extra while flying, the idea of tipping at 35,000 feet might seem absurd.
Yet, the issue regularly comes up as travelers wonder whether it's appropriate or might make a flight more pleasant.
In a recent poll on Airfarewatchdog.com, more than a quarter of respondents—27 percent—said they had tipped a flight attendant at some point during their travels, whether as a thank you for doing a good job or for going out of the way to make them more comfortable.
Etiquette experts caution it's not expected or necessary, and the Association of Flight Attendants says its members don't accept tips.
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But crews say they do sometimes see fliers offer cash and gifts.
Heather Poole, a veteran flight attendant for a major U.S. carrier, said it doesn't happen often, but she has been tipped on flights.
She sees the practice most frequently on Las Vegas routes. Most passengers who try to tip are in economy class, she said.
"It's company policy not to accept tips. That said, it's always appreciated when a passenger makes such a nice gesture," said Poole, the author of "Cruising Attitude: Tales of Crashpads, Crew Drama, and Crazy Passengers at 35,000 Feet."
"Normally, I'll turn it down at least three times, but if someone continues to insist that I accept a tip and then shoves it in my hand or pocket, I might take it. At this point, I feel like it's almost rude not to."
A regular passenger on the New York-Los Angeles route once gave the crew gold hoop earrings during Christmas, Poole recalled. Most tips consist of "a couple of singles," but there's been a time when a passenger presented $50, she added. Many people might be shocked at how little some of her colleagues make, Poole noted.