On September 11, 2001, four US passenger planes were hijacked by al Qaeda in the United States.
Two of those four planes were flown into the Twin Towers in New York City as suicide attacks. The first plane crashed into the North tower at 8:46 ET, and the second plane crashed into the South Tower soon after at 9:03 ET.
Another plane hit the Pentagon in Washington D.C. in a suicide attack at 9:37 ET. The final plane was flown into a field in Pennsylvania. All of the passengers died in the final crash after attempting to regain control of the plane from the hijackers. It's reported that flight 93 was likely headed towards the US Capitol.
Flight 93 was a regularly scheduled flight from Newark, New Jersey to San Francisco, California. On September 11, the flight had 33 passengers and 7 crew members. The plane was delayed in Newark due to flight traffic that morning, but eventually took off and was overtaken by the hijackers around 40 minutes into the flight.
Passengers and crew members on the flight contacted officials and family members on the ground to inform them of the hijacking. A husband of one of the flight attendants on board remembers hearing, "everyone is running to first class." It's understood that while the passengers tried to enter the cockpit, the hijackers chose to crash the plane into a rural field in Pennsylvania.
American Airlines flight 11 was headed to Los Angeles from Logan Airport at 7:59 AM with 76 passengers, 11 crew members, and 5 additional hijackers. The flight crashed into the Twin Towers at 8:46 ET.
United Airlines flight 175 was also heading to Los Angeles from Logan Airport at 8:14 ET. The plane went on to crash into the South Tower.
American Airlines flight 77 was headed to Los Angeles International Airport from Washington Dulles International Airport at 8:20 ET. This plane went on to crash into the West wall of the Pentagon.
In the September, 11, 2001 attacks, 2,996 people were killed. The New York City Fire Department lost almost 350 fire fighters during the attack. 2,753 people were killed in New York, 184 people were killed in the Pentagon, and 40 people were killed on flight 93.