[Tamar1973]

The Yemeni man who was wrestled to the floor after pounding on the cockpit door of a plane approaching San Francisco may have mistaken it for the bathroom.

He must have ignored that presentation the airline staff give at the very beginning of the flight when they point to the restrooms and the exits.

[Army Air Corps]

That, and the safety card includes a diagram of the aircraft. Also, restroom doors do not usually have a sign at eye level reading “No Unauthorized personnel beyond this point” or similar verbiage. He is either a wannabe terrorist or a complete moron (please note, there are not mutually exclusive choices).