I really am not denigrating new yorkers here, but I must confess that I do not understand the reaction.
This isn't intended as a smug comment, so please do forgive me if it sounds so.
I understand that low flying planes are scary, particularly in the circumstances, but I'm not sure what's expected to be achieved by panic and evacuation. If the plane is close enough to be a threat I sincerely doubt that heading to the lifts is going to save the day. If it's not close enough to be a threat, the F-16s will handle it should it look like becoming one. Either way, action is either needless or pointless.
And, before anybody tells me I have no idea what it's like, etc, etc, etc - I work in London, and on the day of the tube bombings was sat in my offices, right above a train station. My boss was out of the country and asked if I was going to evacuate, so I explained that anything that hadn't gone off by 11am probably wasn't going to, and got back on with work.