‘When you have a fire in an aircraft, there’s no place to go, exactly,’ Romney told the LA Times. ‘And you can’t find any oxygen from outside the aircraft to get in the aircraft, because the windows don’t open. I don’t know why they don’t do that. It’s a real problem.’
Mitt Romney, pondering why airplane windows can’t open midflight. There’s nothing like the breeze through your hair at 30,000 feet, amirite folks?

He’s obviously never seen the 1964 James Bond film Goldfinger, or he’d have his answer:
And yes, this can theoretically happen.
So no, Mitt. It’s not a real problem. The real problem is if they DID open. Airplane windows opening midflight would be handy for disposing of Bond villains or unruly passengers, yes, but physics says this is a bad idea.