The United States Air Force officially became it's own branch of the military on September 18, 1947. Up until that day, they were a part of the Army and Navy. This branch is in charge of aerial warfare and defense, and it's only fitting that it's the biggest and most technologically adept air force in the world.
From the early days, things have changed dramatically with the invention of unmanned units saving lives. The USAF has been a part of every major military action in the past century beginning with the World War I spanning through World War II, Cold War, Korea, Vietnam, Panama, Gulf War, and Yugoslavia to current day Afghanistan and Iraq. Though no official motto, this valiant branch's various squadrons all over private mottos including "Un Ab Alt - One over All."
To all the men and women who've chosen to serve in this distinquished branch, thank you for your sacrifice. For those who lost their lives as a result of that service, they will never be forgotten. Everytime another soldier boots up, they're thinking of those who've gone before. Everytime a civilian sees the flag wave, the memory of those lost is there. Thank you.