Airline passengers have one more thing to worry about when they fly— unsanitary practices by flight attendants.

The Food and Drug Administration (FDA) issued a warning to Horizon Air, citing lack of facilities for hand-washing as insufficient for employees who handle food and ice, The Seattle Times reported. The airlines 76-seat airplanes do not have sinks.

The May 13 letter comes after several FDA inspections last winter and correspondence about the issue. While the airline did fix other issues, the employees continued to serve drinks with ice.

“Directing your employees to wash their hands in the airport between flights or to use hand sanitizer does not meet the requirements for suitable lavatory facilities for food-handling employees,” the FDA wrote. “We recommend that you discontinue the use of ice and serve only food and beverages that are in closed containers.”

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It’s unusual to not have sinks on commercial airplanes, one expert said.

“People are in close contact. All it takes is one person with an infection and it can easily spread on an airplane,” Roy Costa, a public-health consultant and trainer who writes about airline food safety told The Seattle Times. “Hand-washing is one of those things you can’t do without.”

According to the Centers for Disease Control and Prevention (CDC), hand washing dramatically reduces the number of people who get sick and studies show hand sanitizers are not as effective. Sanitizers can be effective against bacteria, but “basically don’t work” for viruses, Costa told The Seattle Times.

“If the person handling the ice is infected, and they haven’t washed their hands, that’s going to spread to the ice and eventually to the beverage. You’re talking microorganisms here, viruses that are extremely small and can be huge in number,” Costa told the newspaper. “Without hand-washing, you don’t have any barrier at all.”

Horizon has 15 business days to reply to the FDA’s warning letter, a method reserved for what the agency considers to be significant violations of the law, The Seattle Times reported. If the airline doesn’t resolve the issue, the FDA could pursue legal action.

Horizon Air is owned and operated by Alaska Air Group.

“The safety and health of our customers and employees is our No. 1 priority. We are working with the FDA to revise our in-flight procedures to resolve its concerns. We plan to roll out more robust procedures on all Horizon flights next week,” a spokeswoman said in an emailed statement, The Seattle Times reported.

On Thursday, the airline said flight attendants will now be required to sanitize their hands with what the airline described as hospital-grade disinfectant, then immediately don food-service gloves before serving beverages.