25 years after 9/11: The warnings, ‘muscle hijackers’ and details you may not know

Two hijacked planes cutting through the Manhattan sky into the World Trade Center, a plume of thick smoke rising above the Pentagon, and a shattered field in Pennsylvania: the images of September 11, 2001, remain burned into memory even a quarter-century later.

President George Bush was in Florida on the morning of the 9/11 attacks. Chief of staff Andrew Card entered the classroom where Bush was sitting with children and quietly told him that the second tower was hit. (AP/Reuters)Nineteen al Qaeda terrorists hijacked four commercial aircraft 25 years ago on this day. They turned three of the planes into weapons against the World Trade Center in New York and the Pentagon near Washington. The fourth crashed into a field in Pennsylvania after passengers fought back.

The attacks killed 2,977 people, according to US government records. This figure excludes the 19 hijackers. The tragedy of 9/11, though, began long before the first plane hit.

Osama bin Laden, the founder and leader of al Qaeda, was ultimately held responsible for the attacks. The 9/11 Commission traced al Qaeda’s campaign against the US through the 1993 World Trade Center bombing, the 1998 US embassy bombings in Kenya and Tanzania, and the 2000 attack on the USS Cole.

The 1998 embassy bombings were a turning point. The CIA says Khalid Sheikh Mohammed, later identified by the 9/11 Commission as the principal architect of 9/11, received bin Laden’s approval to plan attacks inside the US less than six months later.

KSM had long considered using aircraft as weapons. The 9/11 Commission identified him as the attack’s principal architect and manager of the “planes operation”.

The men came from different backgrounds, but the plot relied heavily on an al-Qaeda cell based in Germany’s Hamburg. Mohamed Atta, Marwan al-Shehhi and Ziad Jarrah became three of the pilot-hijackers. Hani Hanjour was the fourth.

The other 15 were “muscle hijackers”, tasked with overpowering passengers and crew and taking control of the planes. They travelled through several countries before reaching the US. Several passed through the UAE, where al-Qaeda facilitators helped arrange tickets, traveller’s cheques and hotels.

The 9/11 Commission found that 14 of the 15 muscle hijackers entered the US by the end of June 2001. Most entered on tourist visas.

Several hijackers already triggered US airport security systems.

Mohamed Atta was flagged by security before his flight from Maine's Portland to Boston. Three other Flight 11 hijackers were also flagged in Boston. But the system mainly led to additional baggage checks.

At Washington Dulles, several Flight 77 hijackers also triggered security alerts. Khalid al-Mihdhar and Majed Moqed set off metal detectors. Nawaf al-Hazmi triggered two alarms, was hand-wanded and had his carry-on checked for explosives.

All five still boarded the plane. The 9/11 Commission later described the screening of Moqed and Hazmi as “marginal at best”.

There had been repeated warnings that bin Laden and al Qaeda were planning attacks against the US. The 9/11 Commission later said that by the summer of 2001, “the system was blinking red”.

On August 1, the FBI warned that an attack inside the US could not be ruled out. On August 3, another intelligence warning said the threat of an al-Qaeda attack was likely to continue.

Then, on August 6, President George W Bush received a briefing titled “Bin Ladin Determined to Strike in US”.

On the morning of September 11, Mohamed Atta and Abdul Aziz al-Omari flew from Portland to Boston. Five hijackers boarded Flight 77 at Dulles, while four boarded Flight 93 at Newark.

By about 8am, all four teams were in place. The 9/11 Commission found that the hijackers had successfully passed through the US aviation-security system then in place.

American Airlines Flight 11 left Boston for Los Angeles at 7:59am. Around 8:14am, the crew stopped responding to air traffic control. The 9/11 Commission believes the hijacking began around that time.

Flight attendants Betty Ong and Amy Sweeney called ground staff. They reported that passengers and crew had been stabbed, the cockpit was inaccessible and the attackers had used a substance like mace or pepper spray. The hijackers also claimed they had a bomb.

One hijacker accidentally broadcast, “Nobody move. Everything will be okay,” over the air-traffic-control channel. The hijackers apparently did not realise that controllers on the ground could hear them.

American Airlines Flight 11 hit the North Tower at 8:46 am. The Boeing 767 was carrying a large amount of jet fuel. The impact damaged several floors, structural columns and fireproofing, but the tower remained standing.

The National Institute of Standards and Technology (NIST) later found that the fires weakened the exposed steel. The resulting structural damage eventually caused the tower to collapse.

United Airlines Flight 93 left Newark at 8:42am, more than 25 minutes late. It was scheduled to leave at 8am.

The delay proved crucial. The hijackers had planned the four attacks around departures between 7:45am and 8:10am. Flight 93’s late takeoff gave passengers more time to learn about the attacks on the World Trade Center and understand what was happening.

United Airlines Flight 175 crashed into the South Tower of the World Trade Center at 9:03am. The impact was captured on live television as news networks were already broadcasting images of the burning North Tower.

United 93 was hijacked at 9:28am over eastern Ohio. The cockpit struggle was accidentally broadcast to air-traffic controllers.

The pilot or first officer could be heard shouting for the attackers to get out.

Soon, passengers began calling people on the ground. The 9/11 Commission found that at least 10 passengers and two crew communicated vital information to people on the ground. At 9:57am, the passenger counterattack began.

The passengers made a collective decision to fight back. The hijacker-pilot, Ziad Jarrah, violently rolled and pitched the aircraft in an attempt to stop the passengers from reaching the cockpit.

At 10:02am, the aircraft went into a steep descent. At 10:03:11am, United 93 crashed near Shanksville in Pennsylvania.

The 9/11 Commission concluded that the intended target was probably either the US Capitol or the White House. The passengers prevented the aircraft from reaching Washington.

The Flight 93 National Memorial says the cockpit voice recorder captured the sounds of the struggle. The full audio remains sealed by the FBI.

American Airlines Flight 77 had been hijacked between 8:51 and 8:54am. The aircraft disappeared from conventional radar after its transponder was switched off.

At 9:32am, controllers spotted the aircraft on primary radar. It was about 10 km from the Pentagon at 9:34am when it turned and rapidly descended.

At 9:37am, Flight 77 crashed into the Pentagon at about 900 kmph. All 64 people aboard died, along with 125 people inside the Pentagon.

The US Department of Defence puts the total Pentagon death toll at 189.

The South Tower, which had been struck second, collapsed first. It had been burning for less than an hour.

The collapse killed hundreds of people who had remained inside, including firefighters and police officers who had climbed the tower to rescue others.

The North Tower collapsed at approximately 10:28am. NIST estimated that about 87% of the roughly 17,400 people estimated to have been in the two towers evacuated successfully.

NIST found that 619 people in or above the South Tower’s impact zone died.

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WTC 7 is perhaps the most persistent source of conspiracy theories surrounding 9/11. It was a 47-storey building near the main World Trade Center complex. It was not hit by a plane but collapsed at 5:20pm.

NIST found that debris from the North Tower damaged the building and started fires on several floors. Sprinkler water supplies had also failed, allowing the fires to burn for hours.

The heat caused steel floor beams and girders to expand. This led to the failure of a key structural column, triggering a progressive collapse of the building.

NIST also investigated claims that WTC 7 was brought down by controlled demolition. It found no evidence of explosives or a missile strike on the building or either of the Twin Towers.

President Bush was in Florida on the morning of the attacks. At 9:05am, chief of staff Andrew Card entered the classroom where Bush was sitting with children and whispered that a second plane hit the other tower. Card told Bush: “America is under attack.”

The moment was captured in a photograph that became one of the most recognisable images of 9/11.

The man behind the 9/11 attacks remained at large for nearly a decade. US intelligence gradually tracked his network and identified one of his couriers. By 2010, agencies had linked the courier to a compound in Pakistan's Abbottabad.

On May 2, 2011, US special operations forces raided the compound and killed Osama bin Laden.

(With inputs from the 9/11 Commission Report, National Institute of Standards and Technology (NIST), FBI, CIA, US Department of Defense, US National Park Service/Flight 93 National Memorial, and CDC’s World Trade Center Health Program.)

Anita Goswami is a Senior Content Producer at Hindustan Times, where she primarily covers Indian and international news. With four years of industry experience, she has led coverage of Indian General elections, Assembly elections, and national polls in the United States, Canada, Bangladesh, and Nepal. Her reporting covers global wars and major events, including Operation Sindoor, Sheikh Hasina's ouster and the Mahakumbh Mela. She verifies facts and uses clear sources to ensure accurate reporting. As former Chief Copy Editor at Storytailors, she managed teams to produce top-quality content for networks like NDTV, Profit, CNBC-TV18, Upstox and News18. Her work is featured in NDTV, Meaww, and Global Pulse. Throughout her tenure, Anita has collaborated with and been mentored by top industry experts. When not reading, Anita can be found outdoors or at a bakery. Fields of interest: Indian political history, international elections, historical policy analysis, global conflicts, cultural events, Formula 1, art, media ethics and reporting on socio-political change over time.Read More