That's why you hardly ever see pilots with full beards in the cockpit.
If you have ever looked closely during boarding, you may have noticed something unusual: pilots with large, full beards are extremely rare. While some have short stubble or neat moustaches, long and thick beards remain restricted by many airlines because of safety concerns.
The main issue is the emergency oxygen mask. If cabin pressure suddenly drops or smoke enters the aircraft, pilots must put on their oxygen masks immediately. The mask needs to form a tight seal against the face to work properly, and facial hair can potentially interfere with that seal.
A 1987 study by the US Federal Aviation Administration (FAA) found that the longer the beard, the more difficult it could be for an oxygen mask to seal effectively. The findings led many airlines to introduce strict grooming rules for cockpit crews.
However, later research challenged the idea that beards necessarily make oxygen masks unsafe. In 2018, Air Canada commissioned researchers from Simon Fraser University to test men with different levels of facial hair, including very long beards of up to 40 centimetres.
The results were surprising. Within the conditions tested, researchers found no significant negative effect on oxygen protection, even among participants with beards. Following the study, Air Canada changed its rules and allowed pilots to wear beards, although they must not exceed 12.5 millimetres.
Airlines still have very different policies. Hawaiian Airlines has maintained a strict cockpit beard ban, while European carriers are generally more flexible. Edelweiss allows neatly groomed beards up to 10 millimetres, as does Helvetic Airways. Swiss permits beards of up to 15 millimetres, provided they are clean, neatly shaped and well maintained.
So the next time you board a plane and notice a clean-shaven pilot, it may have little to do with appearance. For many airlines, the grooming rules are closely connected to emergency procedures and the need to ensure that critical safety equipment works as reliably as possible.