As the Air Force celebrates its 67th birthday, here’s seven things you may not know about the most recently formed branch of the U.S. military.

1. The Air Force shares its birthday with the CIA. Both were founded on September 18, 1947.

2. A “roof stomp” is an Air Force tradition where airmen welcome new commander or celebrate a special occasion by climbing up on the commander’s roof and make noise while others are bang on the windows and doors. The commander then opens the door to welcome in the group for refreshments. (In recent years, some airmen have modified the tradition to a “porch stomp.”)

3. Before the Air Force became its own branch of the military, it was a part of the Army. On Aug. 1, 1907, the U.S. Army Signal Corps formed the Aeronautical Division, which later evolved into the Air Force.

4. Each March, some airmen participate in a Mustache March, a tradition where airmen grow mustaches to honor Air Force legend and triple ace Brig. Gen. Robin Olds.

5. Johnny Cash, Morgan Freeman and James Stewert are just a handful of the celebrities who have served as airmen. Stewart - who won an Oscar for “Philadelphia Story” before flying missions in World War II and Vietnam - rose to the rank of brigadier general in the Air Force Reserve.

6. In 1947, then-Air Force Capt. Chuck Yeager broke the sound barrier in his Bell X-1 rocket-powered aircraft, beginning a new era of aeronautics in America.

7. Two U.S. presidents — Ronald Reagan and George W. Bush — served as airmen. Reagan’s service came when the branch was still the Army Air Forces. Bush served in the Texas Air National Guard before transferring to the Air Force Reserve.