I drink more when I'm traveling. It helps alleviate the stress that comes with all of the security crap, long lines, delayed flights, etc. Its much more likely to happen if I'm in an airport with a smoking bar. I've never gotten too drunk to board a plane but I'm quite sure boarding agents could smell the booze on many occasions.

I once met a guy at MSP in a tiny bar nestled in the Intl departure area. (Some of you may know it. It's the one with all the foreign currencies displayed) The guy had gotten smashed and was told he couldn't fly. What does he do? Return to the same bar and have more drinks while waiting to (hopefully) catch the next flight to his destination. The bar owner kept serving him and said he could stay as long as he wanted or until the bar closed. The guys speech was slurred and he was staggering when he tried to walk. Some people never learn.