At 8:46 a.m., American Airlines Flight 11 flew directly over Battalion Chief Joseph Pfeifer’s head and crashed into the north tower of the World Trade Center. He was the first fire chief to reach the building and began sending firemen up the stairwell. He soon discovered that he had no way to keep in touch with the rescuers… his two-way radio was not working inside the high-rise building.
A short time later, Assistant Chief Joseph Callan felt the north tower move and made the decision that the building was no longer safe. At 9:32 a.m., he ordered all units to come out and come down to the lobby. Hardly any firefighters inside the tower responded. Few people had heard the order.
After the south tower fell, a police helicopter saw that the north tower was also in danger of collapse and radioed for an immediate evacuation. Nobody responded. Twenty-one minutes after the helicopter pilot’s warning, the tower collapsed.
The New York Times estimated that at least 121 emergency responders were close enough to the lobby to have exited the building before its collapse.