When the two Boeing 767s crashed into the World Trade Center, fireballs, wreckage, and plane pieces ejected from the towers. Large pieces of the planes, such as an engine and landing gear, were discovered blocks from Ground Zero.
Weeks later, police detectives, FBI agents, and firefighters continued to search through the wreckage for human remains, personal objects, and any clues relating to the terrorists. They desperately wanted to locate the planes’ flight recorders. Each plane had two "black boxes"—a cockpit voice recorder and a flight data recorder—located near the tail. Recovery of any black box would have provided investigators with information on the final minutes of the doomed planes. Posters inside the tents offered various pictures of what the flight recorders could look like if they survived. After almost a year of combing through Ground Zero and the Fresh Kills facility, the staff found some plane pieces, but none of the black boxes. An expert on aircraft construction was on site to help with the identification of the plane parts.