FYI: Helicopters take a bit to get underway. Pilots have to do a safety check, crew must be assembled, gear packed, etc. As helicopter rescue is a rarity, they would most likely NOT be ready at the drop of a hat to get into the air. With a major airport, in a major city, with a helo capable of heavy lift, you're porbably looking of at LEAST an hour's time. Even the biggest civvie choppers cannot hold more than probably 12 people. if there's 300 people on the roof, say, thats at LEAST 25 trips of one chopper. Figure in flight time, load/unload time, and any other variables, its about a 20 minute round trip. So, with 300 folks (mind you, I simply picked a number, not based on anything), you make 25 trips, as 20 minutes apiece, you're looking at a timetable of several hours, just for a roof evacuation. All in all, the numbers simply dont add up. Just head down the damned staircase!!!