This is how fast the U.S. airspace reacted after 9/11. ✈️🇺🇸 Within minutes of the attacks on September 11, 2001, the U.S. aviation system began taking unprecedented action. At 9:25 a.m., the FAA ordered a national ground stop, meaning civilian aircraft across the country could no longer take off. But the response didn't stop there. At 9:45 a.m., the FAA ordered aircraft already in the air to land at the nearest suitable airport as soon as practical. At that moment, more than 4,500 aircraft were flying under instrument flight rules. Think about the coordination required. Thousands of aircraft were already spread across one of the busiest airspaces on Earth. Air traffic controllers had to communicate with pilots, reroute aircraft and bring them down safely while the country was dealing with an unfolding national emergency. And it happened remarkably quickly. By 12:15 p.m., the airspace over the 48 contiguous states was clear of commercial and private flights — an unprecedented s...