I carry a Stanley steel thermos in my carryon luggage. I prefer to get coffee in the lounge at the Hilton and take it to the job site.

I have NEVER had my bag checked for the thermos, even when there was still coffee in it.

Back in 2002, I carried the thermos, a switch box and a set of PS2 cables. I knew that image on the monitor would raise at least an eyebrow, but nada. I guess the machines and the operators are able to discern the difference in a flash.