[1] In the mid-1990s, bin al-Shibh moved as a student to Hamburg, Germany, where he allegedly became close friends with Mohamed Atta, Ziad Jarrah and Marwan al-Shehhi.

He was the only one of the four who failed to obtain a U.S. visa; he is accused of acting as an intermediary for the hijackers in the United States, by wiring money and passing on information from key al-Qaeda figures.

[9] In late 1999, bin al-Shibh traveled to Kandahar in Afghanistan, where he received training at al-Qaeda camps and met others involved in planning the September 11 attacks.

[9] Original plans for the 9/11 attacks called for bin al-Shibh to be one of the hijacker pilots, along with three other members of the Hamburg cell, including Mohamed Atta, Marwan al-Shehhi, and Ziad Jarrah.

[4][11] According to the 9/11 Commission, this refusal of a visa was motivated by general concern by U.S. officials at the time that people from Yemen, which was struggling economically, would illegally overstay their visit and seek work in the United States.

[12][13] Bin al-Shibh was the first to be publicly identified by the United States as the "20th hijacker," someone who was thought to have been tasked to fill out the single missing slot among the four terrorist five-person teams.

[4] In August 2001, bin al-Shibh sent approximately $14,000 to Zacarias Moussaoui, using the alias Ahad Sabet,[14] a few days after receiving transfer of $15,000 from Hashim Abdulrahman in the United Arab Emirates.

[4] According to the Al Jazeera reporter Yosri Fouda's documentary, Top Secret: The Road to September 11, three weeks prior to the attacks, Saeed al-Ghamdi is believed to have used the name "Abdul Rahman" to message bin al-Shibh online (who was posing as a girlfriend), writing a reference to two military/governmental targets and two civilian targets, 19 hijackers and 4 hijacked planes:[15] The first semester commences in three weeks.

Goodbye.Bin al-Shibh later said that Mohamed Atta had phoned him on the morning of August 29 to give a similar coded message revealing the date of the attacks.

[16] After January 14, 2002, bin al-Shibh was featured among five suspected al-Qaeda members on videos delivering what United States Attorney General John Ashcroft described as "martyrdom messages from suicide terrorists.

[18] Ashcroft said the five videotapes, shown by the FBI without sound, had been recovered from the rubble of the home of Mohammad Atef outside Kabul, Afghanistan.

Ashcroft called upon people worldwide to help "identify, locate and incapacitate terrorists who are suspected of planning additional attacks against innocent civilians."

Ashcroft added that an analysis of the audio suggested "the men may be trained and prepared to commit future suicide terrorist acts."

[24] (see current version displaying photos of five terrorists on the remaining martyrdom videos FBI list, as of June 2006)[25] Ramzi bin al-Shibh was one of the four men among the five whose names were known.

[9] Bin al-Shibh was captured in Pakistan on September 11, 2002, after a gun battle in Karachi with the Pakistani ISI and the CIA's Special Activities Division.

On September 6, 2006, U.S. President George W. Bush announced that bin al-Shibh and thirteen other CIA-held, high-value detainees had been transferred to Guantanamo Bay detention camp.

Bin al-Shibh is also wanted by German courts; he had shared a Hamburg apartment with Mohamed Atta, the suspected ringleader of the September 11 hijackers.

Suzanne Lachelier, one of the attorneys and a reserve officer in the Judge Advocate General Corps, offered to wear a hood, in order to be taken to him when the camp authorities initially refused her examination of the prison.

The judge presiding over the commission's pre-trial motions ordered bin al-Shibh and Mustafa al-Hawsawi to undergo mental competency hearings.

On August 24, 2023, Al-Shibh was declared unfit to stand trial by a U.S. tribunal due to his mental state, after lawyers argued 'CIA torture made him delusional and psychotic'.