I watched the video of Mitt Romney, and from my perspective I get that he really didn't know why windows on airplanes don't open. He is admitting to ignorance on the subject. However, the following line "it's a real problem" seems to be discussing the fire on the plane. He's backtracked his train of thought and left everyone else derailed. I do this all the time, weave through multiple layers in a conversation, and it tends to leave people behind who don't also share this ability.
Being ignorant of a subject, even one that is obvious to most folks, is not a crime, nor is it a mark of stupidity. And folks who talk in layers are usually quite smart. The sudden backtrack to the idea of the fire on the plane is a sign that he was fixated on it, which shows his worry (although whether it was for his wife, or for the fact that no freshly widowed bachelor is going to be elected is up for debate) over the incident.
So stop denigrating a man who admits what he doesn't know. It's a hell of a lot better than a man who pretends to know what he does not. There are plenty of things to not like Mitt Romney for, but stupidity isn't one of them. Sure, he's not up to par in many areas, although I think this is more a matter that he hasn't applied himself fully rather than a sign of lack of intelligence. No one can know everything, and it's a good thing when someone freely admits ignorance on a topic.
As an aside, for whatever reason, his wife looks truly pissed off about something. I wonder why?