(Kevin Henderson/U.S. Army)

Happy birthday to the U.S. Air Force, which officially celebrates 76 years of aiming high, flying, fighting and winning on Monday.

On Sept. 18, 1947, the National Security Act of 1947 established the Air Force as a separate military branch. It is the second youngest branch of the U.S. armed forces after the U.S. Space Force, which was founded in 2019 and also falls under the Department of the Air Force.

However, the branch’s roots trace back to 1907, when the U.S. Army Signal Corps established an aeronautical division to take “charge of all matters pertaining to military ballooning, air machines, and all kindred subjects,” according to the Air Force Historical Research Agency. The Army’s first airplane came in 1909, and by the time World War I broke out in Europe in 1914, the 1st Aero Squadron had 12 officers, 54 enlisted men and six aircraft. Those numbers would increase throughout the war.

In 1926, the Army Air Service became the Army Air Corps. By the end of World War II in 1945, the Air Corps had more than 2 million service members and over 63,000 planes, according to the Air Force fact sheet.