United Airlines Flight 175 was a scheduled U.S. domestic passenger flight from Logan International Airport in Boston, Massachusetts to Los Angeles International Airport. It was hijacked by five Islamic terrorists and deliberately flown into the South Tower of the World Trade Center in New York City as part of the September 11, 2001 attacks. Over thirty minutes into the flight, the hijackers forcefully breached the cockpit and overpowered the pilot and first officer. Marwan al-Shehhi, who was trained as a pilot, took over the controls. Air traffic controllers noticed the flight was in distress when the crew stopped responding to them. Several passengers and crew aboard made phone calls from the plane and provided information about the hijackers and injuries to passengers and crew.
The aircraft crashed into the South Tower of the World Trade Center at 09:03, killing all 65 people aboard, including the hijackers. The crash was seen on live television. The impact and subsequent fire caused the South Tower to collapse, which resulted in hundreds of additional casualties. During the recovery effort at the World Trade Center site, workers recovered and identified remains from Flight 175 victims, but many other body fragments could not be identified. The flight was the second plane hijacked and flown into the World Trade Center, but was the one airline crash that morning to be witnessed live on television around the world as it happened. It was preceded by American Airlines Flight 11, which had struck the top of the North Tower 17 minutes earlier.
Hijackers Ahmed al-Ghamdi and Hamza al-Ghamdi checked in at the United Airlines counter at Logan International Airport at 06:20 Eastern Time. Ahmed al-Ghamdi checked in two bags. Both hijackers had trouble answering the standard security questions. The counter agents repeated the questions slowly until the men gave the correct answer. Hijacker pilot Marwan al-Shehhi checked in a single bag at 06:45 and the two remaining hijackers, Fayez Banihammad and Mohand al-Shehri, checked in at 06:53. Banihammad checked two bags. None of the hijackers were selected for extra scrutiny by the Computer Assisted Passenger Prescreening System (CAPPS). Shehhi and his team boarded Flight 175 between 07:23 and 07:28. Banihammad boarded first and sat in first class seat 2A with Shehri in 2B. At 07:27, Shehhi and Ahmed al-Ghamdi boarded and sat in business class seats 6C and 9D respectively. A minute later, Hamza al-Ghamdi boarded and sat in seat 9C.
The flight was scheduled to depart at 08:00 and left the gate at 07:58. The flight departed at 08:14 and reached its cruising altitude 31,000 feet. At 08:37, air traffic controllers asked the pilots of UA175 whether they could see American Airlines Flight 11. The crew responded that the hijacked flight was at 29,000 feet and controllers ordered Flight 175 to turn and avoid the aircraft. The pilots declared that they had heard a suspicious transmission upon takeoff. "Sounds like someone keyed the mike and said everyone stay in your seats," the flight crew reported. This was the last transmission from Flight 175.
At around this time, the flight had a near midair collision with Delta Air Lines Flight 2315, reportedly missing the plane by only 200 feet, as air traffic controller Dave Bottiglia frantically tried to tell the Delta pilot to take evasive action. Bottiglia was the first person in the control center to realize that Flight 175 was hijacked when he gave directions for a turn. Flight 175 did not respond, it instead accelerated and headed toward Delta Air Lines Flight 2315. The controller commanded the Delta pilot, "Take any evasive action necessary. We have an airplane that we don't know what he's doing. Any action at all. When the plane passed by, the control center added Flight 175 to the list of hijacked planes.
In five minutes, there was no doubt of an emergency, as the plane had radically changed course and was not responding. Despite reports that one of the passengers called his mother and told her they were thinking of storming the cockpit, it appears that no such intervention took place.
By 8:58, the plane was heading towards New York City and descended from an altitude of 28,500 feet over New Jersey. From the time al-Shehhi completed the turn toward New York (approximately 8:58) to the moment of impact (9:02:40), the plane went into a sustained power dive, descending more than 24,000 feet in 4 minutes 40 seconds, for an average rate of over 5,000 feet per minute. New York Center air traffic controller Dave Bottiglia reported he and his colleagues "were counting down the altitudes, and they were descending, right at the end, at 10,000 feet per minute. That is absolutely unheard of for a commercial jet."
Three passengers, Peter Hanson, Brian David Sweeney, and Garnet Bailey made phone calls, all from GTE airphones, from United Airlines Flight 175. Flight attendant Robert Fangman also made phone calls.
At 8:52 a.m., Peter Hanson called his father, Lee Hanson in Easton, Connecticut, telling him of the hijacking. Hanson was traveling with his wife, Sue, and 2 1/2 year old daughter, Christine. Hanson said that the hijackers had commandeered the cockpit, that a flight attendant had been stabbed, and possibly someone else in the front of the aircraft had been killed. He also reported that the plane was flying erratically.
Flight attendant Robert Fangman called a United Airlines office in San Francisco, and spoke with Marc Policastro. He reported the hijacking, and said that both pilots had been killed. He also reported that a flight attendant was stabbed, and said that the hijackers were flying the plane. The call was disconnected after a minute and 15 seconds.
At 8:58 a.m., Brian David Sweeney tried calling his wife, Julie, and left her a message, telling her that the plane had been hijacked. He then called his parents at 9:00 a.m., and spoke with his mother, Louise. Sweeney told his mother about the hijacking, and mentioned that passengers were considering storming the cockpit and taking control of the aircraft.
Peter Hanson made a second phone call to his father at 9:00 a.m.
"It's getting bad, Dad. A stewardess was stabbed. They seem to have knives and Mace. They said they have a bomb. It's getting very bad on the plane. Passengers are throwing up and getting sick. The plane is making jerky movements. I don't think the pilot is flying the plane. I think we are going down. I think they intend to go to Chicago or someplace and fly into a building. Don't worry, Dad. If it happens, it'll be very fast....Oh My God.., oh my God, oh my God."
As the call abruptly ended, Hanson's father heard a woman screaming.
Then at 9:01 AM; two minutes before impact as United 175 continued its descent into Lower Manhattan, New York Center alerted another nearby Air Traffic Facility responsible for low flying aircraft. As the flight neared the World Trade Center, ATC was able to monitor the flight's impact path.
At 9:03, Flight 175 crashed into the southern facade of Tower 2 of the World Trade Center (south tower), traveling at approximately 545 mph and impacting between floors 77 and 85 with approximately 10,000 gallons of jet fuel. Onboard were 56 passengers (including the 5 hijackers) and 9 crew members, none of whom survived. Hundreds more were killed within the tower and from its ensuing explosion, fires, and collapse. Around 600 people were killed instantly or trapped at and above the floors of impact in the South Tower.
According to eyewitnesses and video footage, the aircraft appeared to execute a banking left turn in the final moments, as it appeared that the plane might have otherwise missed the building or merely clipped it with its wing. Upon crashing, the plane was banked left. Those seated on the left side of the plane would, therefore, have had a clear view of the towers approaching, with one burning, until the final moment of the flight.
The image of the crash was caught on video from multiple vantage points on live television and amateur video. Video were continually replayed in news broadcasts over the next few days. A very clear photo was taken by Carmen Taylor from the top deck of the Ellis Island Ferry moored in Battery Park. The NIST collected over 200 photos and 40 videos.
Unlike at the North Tower, initially, one of the three stairwells was still intact. Only 18 people passed the impact zone through the available stairway and left the South Tower safely before it collapsed. One of those 18 people, Stanley Praimnath was on the 81st floor and witnessed Flight 175 coming towards him. Some people above the impact zone made their way upward toward the roof in hope of a helicopter rescue. However, access doors to the roof were locked. In any case, thick smoke and intense heat prevented rescue helicopters from landing.
At 9:59:04 the south tower of the World Trade Center collapsed.
Shortly after the crash, the flight number for future flights on the same route was changed from Flight 175 to Flight 1525 "out of respect for those who died in the attack". Since then, United Airlines has renumbered and rescheduled all flights from Boston to Los Angeles, and none of its morning flights depart at 8:00 AM EDT. As of September 2007, this flight has now been redesignated as Flight 163, which now operates as a Boeing 757-200.