Book(s), a place to refill my water bottle, munchies, and working bathrooms and environmental controls, and I'm good. For a complete screwup, add in water purifier tablets and a change of clothes. I got stuck on a train a couple of years back with no air condition, no flushing toilet, and a 5 hour delay. The water bottle and a pair of shorts and t-shirt made life easier for me then most of the other passengers.

A couple of people are going to get clobbered for this one. The 7 hour AmericanAirlines delay was the fault of US Customs who refused to let anybody deplane from the Paris flight. I don't know what happened with the Jetblue flights since that was domestic.