The flight crew of Flight 175 makes their last transmission to air traffic control. At some point in the next four minutes, the hijackers get their second plane. We know little about the takeover of the cockpit of Flight 11, but the hijacking of Flight 175 was bloody and violent. Both pilots are killed.
At around this time, Flight 11 and Flight 175 nearly have a mid-air collision, 55 miles north of New York City.
Also at this time, United Airlines Flight 93 takes off from Newark International, bound for San Francisco. The flight is 41 minutes late getting off the ground.
So far, nothing has been reported in the media. In four minutes, that will change.