The low-cost airline introduced a tipping function three years ago, including an option to add gratuity on the digital tablets used to order food and drinks on its flights.

Until recently, however, the tips were pooled amongst all of the flight attendants. But following a push from flight attendants, as of Jan. 1 of this year, each person will keep the tips they make from their own sales.

“We appreciate the great work of our flight attendants and know that our customers do as well,” said Frontier spokesman Jonathan Freed. The option to tip is “entirely at the customer’s discretion, and many do it,” he added. The option to add gratuity is also at the discretion of the flight attendant: they can choose whether or not to trigger the option on the tablet.

Not everyone is happy with the change, however. The Association of Flight Attendants International, which represents 50,000 flight attendants at 20 airlines, opposes the practice in its entirety.

It has noted that the responsibility of flight attendants is to ensure the safety and security of a flight’s passengers and shouldn’t be affected by tips. Furthermore, the Association has contended that the tipping option has been used to weaken its contract negotiations. It has been negotiating a new contract with Frontier for the last two years.

While the airline has not disclosed how much flight attendants have earned through the tipping system, Freed emphasized to The Los Angeles Times that tips are seen as “additional compensation over and above” their wages.