If you’ve been on a U.S. Air Force installation recently, you may have noticed things looking a little more hairy. The collective groan heard around the world on March 1 from significant others and spouses came to you courtesy of Mustache March.

Every March, airmen around the world sport their ’staches in honor of Col. Robin Olds, a fighter pilot ace who flew sorties and missions in World War II and Vietnam. Olds’ trademark handlebar mustache was grown as a symbol of silent defiance of senior leadership. With his streak of incredible luck in combat, fellow airmen began growing “bulletproof mustaches” out of superstition and solidarity.

This good-natured tradition has grown throughout the years. In 2014, former Air Force Chief of Staff Gen. Mark Welsh issued a branch-wide challenge, encouraging the Major Commands (MAJCOMs) to participate and go all in. Many groups and squadrons use this event as a way to fundraise for service-related charities.

Participants in Mustache March must adhere to Air Force Instructions 36-2903, section 3.1.2.2: “… they will be conservative (moderate, being within reasonable limits; not excessive or extreme) and extend downward beyond the lip line of the upper lip or extend sideways beyond a vertical line drawn upward from both corners of the mouth.”

For the spouses whose husbands are participating in this furry ritual, just know that it may be for a good cause, and they are joining in a decades-old Air Force tradition. Hang in there … at the time of publishing, you only have 28 days left.