A well trained individual, usually in the military or almost to retirement stage with the military, who boards planes with regular passengers to ensure that there is not anybody bringing hostility to the environment. Most air marshalls carry a case such as an organ donation case or hard silver box with classfied information. They also board planes with suspected criminal violaters, or major drug dealers to see what's their routines.
My moms neighbor was an air marshal and you would have never guessed. Coincidentally, I sat next to him on a plane from New Orleans to Scottsdale about 6 months ago and it was then that showed me his air marshall paperwork.
at 12:37 PM on Apr. 13, 2009