The aircraft involved, a Boeing 767-200 carrying 51 passengers and 9 crew members (excluding the 5 hijackers), was deliberately crashed into the South Tower of the World Trade Center in New York City, killing everyone aboard and causing the deaths of more than 600[c] people in the South Tower's upper levels in addition to an unknown number of civilians and emergency personnel on floors beneath the impact zone.

Twenty-eight minutes into the flight, the hijackers injured several crew members, forced their way into the cockpit, and murdered both pilots while moving anyone who remained to the rear of the aircraft.

Lead hijacker Marwan al-Shehhi, who had trained as a pilot for the purposes of the attacks, was able to usurp the flight controls once the captain and first officer were eliminated.

Thus, the aircraft was visible on New York Center's radar, which depicted the deviation from its assigned flight path before controllers took notice four minutes later at 08:51 EDT.

Upon realizing, the ATC workers immediately made several unsuccessful attempts to contact the cockpit of the hijacked airliner, which twice nearly collided with other planes as it recklessly flew toward New York City.

In the interim, three people were able to get through to their family members and colleagues on the ground, passing on information to do with the hijackers as well as casualties suffered by the flight crew.

Media coverage of the disaster that began in the North Tower 17 minutes earlier meant Flight 175's impact at 09:03 was the only one of the four attacks to be televised live around the world.

The team was assembled by al-Qaeda leader Osama bin Laden, who also provided the financial and logistical support, and was led by Khalid Sheikh Mohammed, who devised the plot.

The World Trade Center was chosen as one of the targets due to it being a prominent American symbol that represented economic prowess.

[2] During interrogations after his capture, Khalid Sheikh Mohammed stated that he was surprised when both towers were hit, as al-Qaeda had originally only intended to target one.

The reason for the change in target is unknown, though analysts who have reviewed the FBI's evidence noted that Atta and al-Shehhi were very close and may have chosen to "die together".

The hijackers on Flight 175 included Fayez Banihammad, also from the UAE, and three Saudis: brothers Hamza and Ahmed al-Ghamdi, as well as Mohand al-Shehri.

[5] Out of the 60 occupants (excluding the five hijackers), there were 50 Americans, 3 Germans, 2 Britons and one each originating from Iran, Israel, Indonesia, Ireland, and Canada.

The youngest person on Flight 175 was Christine Hanson, aged two and a half;[9] the oldest 82-year-old Dorothy DeAraujo of Long Beach, California.

[21] By 08:42, Flight 175 made the transition to the airspace of New York Center, allowing the pilots to report the suspicious transmission they heard while climbing out of Logan.

"Sounds like someone keyed the mic and said 'Everyone stay in your seats'," Saracini told Dave Bottiglia, the controller dealing with Flight 11.

[23][20] The hijackers launched their assault seconds later at 08:42, and were in full control of the plane by 08:46, around the same time Flight 11, had already crashed into the North Tower.

[24] Investigators believe that the al-Ghamdi brothers forced the passengers and crew to the aft of the plane by terrorizing them with knives and bomb threats, while also spraying mace into the confines of the cabin.

[20][25] The first operational evidence that something was abnormal on Flight 175 came seconds after the North Tower was struck, when the plane's transponder signal changed twice within the span of one minute, and the aircraft began deviating from its assigned course.

[31] Flight attendant Robert Fangman and passengers Peter Hanson and Brian David Sweeney made phone calls from GTE airphones in the rear of the aircraft.

[32][33] At 08:52, Robert Fangman called a United Airlines maintenance office in San Francisco and spoke with Marc Policastro.

[5] Brian David Sweeney tried calling his wife, Julie, at 08:59, but ended up leaving a message letting her know the plane had been hijacked.

Speaking softly, Hanson said the hijackers had commandeered the cockpit, a flight attendant had been stabbed, and that possibly someone else in the front of the aircraft had been killed.

[27] The airplane crashed nose-first into the South Tower's southern façade at a speed of around 587 miles per hour (945 km/h; 262 m/s; 510 kn),[d] striking through floors 77 and 85[41][42] with approximately 9,100 U.S. gallons (34,000 L; 7,600 imp gal) of jet fuel on board.

[50] The initial assumption was that the crash of Flight 11 had been an accident, a mistaken belief that also hindered the process of immediately evacuating the South Tower after the first plane struck the North.

An estimated 300 people survived the crash, but were trapped by the catastrophic damage done to the skyscraper as well as the heat, fire, and smoke filling its upper levels.

This was because Flight 11 crashed almost directly midway into the North Tower's central core and severed all escape routes from the 92nd floor up, but al-Shehhi flew the plane into the eastern half of the South Tower's southern facade near the southeast corner while also banking at a severe angle, narrowly missing Stairwell A in the northwest corner.

[57][58] Smoke, isolated fires and hot gases ventilating through the stairs compelled those who were trapped to either avoid using them entirely, or to head upward in the hopes of a rooftop rescue,[59] while it has been suggested that others may have been in the process of descending from the impact zone when the tower collapsed at 09:59.

It was reported in May 2011 that the company was reactivating them as a codeshare operated by Continental Airlines, sparking an outcry from some in the media and the labor union representing United pilots.

[88][87] Only one lawsuit progressed to a civil trial; a wrongful death filing by the family of Mark Bavis against the airline, Boeing, and the airport's security company.