On This Day in 2001: September 11

On this day in 2001, four hijacked airliners were flown into the World Trade Center, the Pentagon and a field near Shanksville, Pennsylvania. Nearly 3,000 people died. Both towers came down within two hours of the first impact, and the country's entire commercial airspace was cleared and grounded by early afternoon.

Underneath the national story was a logistical one that repeated in every affected city. Cell networks saturated within minutes as everyone called at once, so most people could not reach their families. Bridges, tunnels and transit closed, and hundreds of thousands walked out of Lower Manhattan on foot, many of them miles, in office shoes. In the weeks after, air quality around the site became its own long running health problem for residents and responders.

Those are the parts a household can actually prepare for, whatever the cause turns out to be. Phone networks fail under load before they fail from damage, a text often lands when a call will not, and a family that has agreed in advance on where to meet does not need the network at all. That agreement is the point of an emergency meeting spot, and the walk itself is why a get home bag lives at work rather than at home.