The mission became a partial failure when the passengers fought back, forcing the terrorists to crash the plane in Somerset County, Pennsylvania, preventing them from reaching al-Qaeda's intended target, but killing everyone aboard the flight.

Ziad Jarrah, who had trained as a pilot, took control of the aircraft and diverted it back toward the East Coast, in the direction of D.C. Khalid Sheikh Mohammed and Ramzi bin al-Shibh, considered principal instigators of the attacks, have claimed that the intended target was the U.S. Capitol Building.

United Airlines Flight 93 was the fourth and final passenger jet to be commandeered by terrorists on September 11, and the only one that did not reach a target intended by al-Qaeda.

[2] Construction of a permanent Flight 93 National Memorial was dedicated on September 10, 2011,[3] and a concrete and glass visitor center (situated on a hill overlooking the site)[4] was opened exactly four years later.

[17] This close contact upset Mohamed Atta, the tactical leader of the plot, and al-Qaeda planners may have considered another operative, Zacarias Moussaoui, to replace him if he had backed out.

The first, Ahmed al-Nami, arrived in Miami, Florida, on May 28, 2001, on a six-month tourist visa with United Airlines Flight 175 hijackers Hamza al-Ghamdi and Mohand al-Shehri.

[26] The seven crew members were Captain Jason Dahl (43), First Officer LeRoy Homer Jr. (36), flight attendants Lorraine Bay, Sandra Bradshaw, Wanda Green, CeeCee Lyles, and purser Deborah Welsh.

[27] At 5:01 a.m. on the morning of September 11, Jarrah placed a cell phone call from Newark to Marwan al-Shehhi, the hijacker pilot of United Airlines Flight 175, in Boston, which authorities believe was to confirm that the plan for the attacks was proceeding.

Before boarding the plane, Jarrah made five telephone calls to Lebanon, one to France, and one to his girlfriend in Germany; he had sent a farewell letter the day before to say he loved her.

[26][31] Many of those aboard Flight 93 would have had a view of the Twin Towers of the World Trade Center complex in New York City, located several miles away across the Hudson River.

[24] With the attacks unfolding, air traffic officials began issuing warnings through the Aircraft Communication Addressing and Reporting System (ACARS).

[38] At 09:24, Flight 93 received Ballinger's ACARS warning, "Beware any cockpit intrusion – two a/c [aircraft] hit World Trade Center".

The hijackers on those flights had waited no more than half an hour to commandeer the aircraft, most likely striking after the seat belt sign had been turned off and cabin service had begun.

"[47] The commission believed Jarrah tried to make an announcement to the passengers, but pressed the wrong button, sending the message to Cleveland controllers; Mohamed Atta had made the same error on Flight 11.

[51] Sandy believes that Dahl took actions to interfere with the hijackers, including possibly disengaging the autopilot, and rerouting the plane's radio frequency so that Jarrah's attempts to communicate with the passengers were instead transmitted to air traffic controllers.

"[54] At 09:39, two minutes after Flight 77 impacted the Pentagon, air traffic controllers overheard Jarrah say, "Ah, here's the captain: [sic] I would like you all to remain seated.

[61] The true nature of the mission came to light only six minutes after the hijacking commenced, when Burnett's wife informed him of the attacks on the World Trade Center.

[65] Jeremy Glick called his wife at 09:37:41 from row 27 and told her the flight was hijacked by three dark-skinned men who looked "Iranian", wearing red bandanas and wielding knives.

[28]: 104–105 The plane then crashed into an empty field in Stonycreek, Pennsylvania, about 20 minutes' flying time from Washington, D.C.[31] The last entry on the voice recorder was made at 10:03:09.

[84][85] Vice President Dick Cheney, in the Presidential Emergency Operations Center deep under the White House, authorized Flight 93 to be shot down, but upon learning of the crash, is reported to have said, "I think an act of heroism just took place on that plane.

[88] Far-flung debris that made up a third of the aircraft, including the cockpit, continued into the woods, demolishing trees on 163 acres (66 ha) owned by the Lambert family,[89] and damaging the nearby residence of Barry Hoover.

The National Transportation Safety Board reported that the flight impacted at 563 mph (489 kn; 252 m/s; 906 km/h) at a forty-degree nose-down inverted attitude.

[105][106] In September 2011, shortly before the 10th anniversary of the attacks, a video of the rising smoke cloud filmed by Dave Berkebile (who had died the previous February) from his yard on Bluebird Lane, 5.8 miles (9.3 km) away from the crash site, was published on YouTube.

[112] Investigators found very light debris including paper and nylon scattered up to eight miles (13 km) from the impact point in New Baltimore.

The FBI initially refused to release the voice recording, rejecting requests by Congresswoman Ellen Tauscher and family members of those on board.

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.

[149] Based on testimony from captured al-Qaeda member Abu Zubaydah, U.S. officials believed the White House was the intended target.

[150] A post-9/11 interview with Khalid Sheikh Mohammed and bin al-Shibh by Al Jazeera reporter Yosri Fouda said Flight 93 was heading for the Capitol.

John Farmer, Senior Counsel to the 9/11 commission, pointed out that this would have been impossible, as Hutchison's squadron was not in the air until 10:38, thirty-five minutes after Flight 93 had crashed.

[171] On the sixteenth anniversary of the crash, Vice President Mike Pence spoke at the memorial: "Without regard to personal safety, they [the victims] rushed forward to save [our] lives ...