For many, tipping workers such as waitstaff, hairdressers or taxi drivers is expected. But one airline is asking passengers to tip their individual flight attendants, too.

When passengers on budget carrier Frontier Airlines buy in-flight food or drinks, they'll now find a space on their payment tablet to leave a tip for the flight attendant that served them. This change was effective Jan. 1. Previously, any tips were pooled.

Tipping flight attendants is uncommon, JT Genter of travel site The Points Guy tells CNBC Make It. On a recent flight on Frontier, Genter was surprised when he was prompted to tip on the digital tablet after purchasing a can of ginger ale.

"I've flown more than 350 flights on 51 different airlines in the past three years, but I'd never experienced an airline ask for a tip," Genter says.

Flight attendants at United Airlines are not allowed to accept tips, and American Airlines crew members are instructed to decline tips, Marketwatch reports. Meanwhile, Southwest Airlines discourages tipping, but flight attendants are allowed to accept voluntary tips if the customer insists.

"It was considered inappropriate and undignified and most airlines forbade tipping or soliciting tipping, although of course it did happen now and then," George Hobica, travel expert and founder of Airfarewatchdog.com tells CNBC Make It. "Most cabin crew would far prefer that a passenger write a letter of commendation to the airline to reward excellent service."

Cabin crew is primarily there for passenger safety, points out Hobica. Shifting that focus could lead to mixed messages and strain the passenger-crew relationship, he says.

Hobica recalls one incident in first class on one major carrier where a passenger rudely demanded a flight attendant's attention. "When [the passenger] wanted a refill of his cocktail he bellowed to a passing flight attendant, 'More ice!,'" Hobica says. "The flight attendant said, 'Sir, what's the magic word?' And he replied: 'Don't teach me manners just give me more ice.'"

Explains Hobica, "I worry that if a flight attendant accepts a tip, then passengers will treat [that attendant] like a servant and not as someone who might save [their] life in an emergency."

Complicating matters is the guilt that can come along when passengers are prompted to give a gratuity for yet another service after they've already paid a lot of money for a ticket. That can put passengers in an uncomfortable position.

"Tipping is one of the most stressful and confusing aspects of etiquette today. It is a significant way to show appreciation for a job well done; however, treating the person who has served you with respect is every bit as important," The Emily Post Institute, a popular etiquette resource, says on its site. (The site does not offer recommendations for how much to tip flight attendants, though it does suggest anywhere from 10 percent to 15 percent for food service. However, as Hobica points out, flight attendants are not waitstaff in the sky.)

Frontier's tipping policy has been met with backlash from the Association of Flight Attendants, an organization that represents 50,000 flight attendants at 20 airlines, including Frontier. The organization opposed the tipping function altogether when it was introduced around three years ago, with AFA president Sara Nelson saying in a statement recently that it was an effort used to "dissuade Flight Attendants from standing together for a fair [compensation] contract — and in an effort to shift additional costs to passengers."

Genter of The Points Guy, an avid traveler, says he's not a fan of Frontier's tipping policy after learning that it was initially introduced as an alternative to increasing flight attendant wages according to the Association of Flight Attendants. A Frontier spokesperson has argued, "We view tips as additional compensation over and above flight attendants' contractual wages."

"I don't mind travelers tipping flight attendants, but it comes across as unprofessional for flight attendants to be requesting tips and for their pay to be not-insignificantly tied to their on-board tips," Genter says.

In 2017, flight attendants made a median pay of $50,500 per year, according to data from the Bureau of Labor Statistics. However, the BLS notes that the lowest 10 percent earned less than $26,680 while the highest 10 percent earned more than $79,520.

Those worried flying just got more complicated, should note that experts doubt tipping will spread to other airlines. That said, Frontier's passengers are tipping on paid food and drink — offerings that used to be free on many airlines not that long ago

Don't miss: Dwyane Wade vs. Gabrielle Union: Here's who is the better tipper in this famous marriage

Like this story? Subscribe to CNBC Make It on YouTube!