A bit of an inappropriate question to ask, maybe, and one that I'm not entirely comfortable asking (in fear of rude comments or accusations), but i'm curious to know the answer, so here goes:

Flew WTP last night LHR-JFK and was seated all by myself in 28B, right by the emergency exit with pleeeeeenty of legroom and no seat next to me...

On another flight a couple of weeks ago, two teenagers who sat next to me (we were also seated in the exit row, but in economy) were joking about "what would happen if we open the emergency exit door mid-air?" and asked (which i at the time thought was a stupid question) how an airline could be sure that those seated at emergency exits aren't lunatics (or, even worse, as they said: had just experienced their girlfriend breaking up with them and wanted revenge)...? and: does the emergency exit door actually open mid-air?

Fast forward again to last night in my semi-comfy WTP seat by the emergency exit and these comments popped up in my head. A few hours into the flight, with 90% of the cabin snoring away and lights dimmed, i asked myself the same question: could this door be opened mid-air? or would i be prevented by some automatic lock that kicks in? who would know that it isn't a real emergency and that i needed to get out?

The uncomfortable question that came to mind was: if the door in fact can be opened mid-air (which i still don't know the answer to), and leaving lunatics and broken hearts aside, why would a potential terrorist (someone who knows exactly what they're doing) go through the hassle of bothering to bring explosives on board? why not just pre-select an emergency exit row and do as the safety card in the seat pocket in front of him/her says?

Just curious to know...