Hey, if it happens, I'll take advantage. If not, oh well.
As for the uniform while traveling...there isn't a single regulation that spans across all branches of the U.S. military. That decision rests within different chains of command within each service. For example, AETC (the Air Force's training command) has a policy that requires members to wear their uniform while traveling within the continental U.S. on official USAF
business. That requirement can be disregarded for trips that will connect with international flights or when duration of travel would be prohibitive to promoting a positive image in uniform.
By the way, travel in uniform is more of a recruiting thing than anything else. I just don't see how someone could perceive a few uniforms on a plane to be a benefit to security. Any half-witted hijacker would know that an ordinary service member isn't allowed any more freedom to carry a weapon than every other passenger.