<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by SarahWest:
I often sit in exit row seats and have thought about this myself. On the 737 I was on last Friday the exit doors over the wings hinged at the top and very definitely opened outwards - so the higher cabin pressure compared to outside would aid opening the door at altitude. What is there to stop some lunatic opening these doors in flight?</font>
Look closer at the design. The doors are hinged such that they have to go inward before they can go outward. Probably the best place to witness this on any sort of plane is sitting at the exit row right next to door two on the 757 (row nine on UA, not sure about other airlines).