I have three of the Think Tank rolling cases, the International, Security, and Logistics Manager. The International fits easily into the overhead or under the seat, carries a huge amount of gear, and looks nothing like a camera case. It does have the TSA lock, which might be an issue, and it's a soft case which could be cut open with some effort.
It can carry 2-3 pro-size cameras, the larger f/2.8 lenses, and other accessories with ease.