The study, conducted by researchers at Embry-Riddle Aeronautical University and published in the journal Aerospace Medicine and Human Performance, found no difference in oxygen saturation levels between clean-shaven pilots and those with short or long beards when they use standard airline oxygen masks.

“Using a current on-demand airline oxygen mask, oxygen saturation levels were never compromised by any of the beard conditions,” the researchers concluded in April. “These results support the contention that airline pilots with beards of any length would not be impaired by hypoxia or smoke while dealing with an in-flight emergency.”

The study involved 24 volunteers who were tested in a hypoxia chamber simulating conditions at 30,000 feet altitude. Participants wore oxygen masks in three beard conditions: clean-shaven, short beards under about 0.4 inches in length, and long beards over 0.4 inches. Their blood oxygen levels were continuously monitored, and researchers found no significant differences between the groups.

Additionally, when exposed to pungent smelling salts with masks on, none of the participants could detect the scent, regardless of facial hair. This suggests beards do not interfere with the mask’s ability to block smoke or other irritants.

These findings align with a 2018 study commissioned by Air Canada, which led the airline to change its policy and allow pilots to have beards. That research, conducted at Simon Fraser University, similarly found that beard length had no impact on the effectiveness of pilot oxygen masks.

Many major U.S. airlines still prohibit pilots from having beards, citing safety concerns about oxygen mask seals. Carriers like American, Delta, United, Southwest, JetBlue, and Spirit require pilots to be clean-shaven, while some others like Hawaiian, Avelo, and Allegiant do allow facial hair.

The FAA does not mandate that pilots be clean-shaven. This rule is usually set by the carrier itself.

Editor's note: This article first appeared on AirlineGeeks.