US-based Frontier Airlines has started asking passengers to tip their cabin crew.

The revelation was spotted by flight blogger JT Genter in The Points Guy.

Genter said that in 350 flights on 51 different airlines he had never been asked to tip crew before.

After ordering refreshments on the airline, passengers are handed a mobile tablet, which prompts them to add gratuity to their bill.

According to Frontier, flight attendants will now earn tips on their individual sales.

You tip your waiter, your bartender, your delivery driver, and basically anyone in a hotel — but how about your in-flight cabin crew?

Chances are, probably not. Until now.

US-based Frontier Airlines has started asking passengers to tip their cabin crew after they bring refreshments around the plane.

The revelation was spotted by popular flights blog The Points Guy after one of its writers flew with the domestic airline.

The author of the blog post, JT Genter, said he was handed a mobile tablet by a flight attendant after ordering his drinks. The tablet prompted him to tip the crew with handy buttons for 15%, 20%, or 25% of his bill and another for "custom gratuity."

The mobile tablet which prompts passengers to leave a tip. JT Genter / The Points Guy

"Gratuities are appreciated!" a message reads on the screen, which Genter photographed. However, there is, of course, an option for leaving no gratuity at all.

"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 wrote.

A Frontier spokesperson told TPG: "Currently tips are shared amongst all members of the flight attendant crew on a given flight.

"Effective January 1, 2019, flight attendants will earn tips on their individual sales."

The ultra-low-cost airline also told Genter that no portion of the tips was kept by the company itself.

Asked if gratuities were meant as extra earnings for flight attendants or "considered a consequential part of their earnings," Frontier told Genter: "Both. Many flight attendants see the in-flight tip program as a way to supplement their income."

It is, as yet, unclear how popular the scheme is with passengers and flight staff, but if it takes off then you may soon see a gratuity charge coming to a budget airline near you.