Well you've all heard about the kerfuffle about "flak" vs "flack." Well, the dictionary says either is correct, and actually...
So does the Army. There are multiple places on Army.mil where it is spelled that way:
http://www.army.mil/...
http://www.army.mil/...
http://korea50.army.mil/...
Is Senator McCain mocking the army? Our troops? Why does he hate our freedom? (and our flack jackets)
And thanks to Senator Obama for fighting back, however you spell it!