Indeed, I made a major faux pas. My posted picture was indeed NOT taken on an aircraft. Apologies! To the best of my ever-failing memory, I took this picture during last summer's trip to Seattle in one of their "light rail" cars.

Regardless of when or where it was taken, the question remains: if you were in an emergency -- and needed to escape from wherever you were -- would you have a clue what this sign meant? I wouldn't!