Already long-time affiliates of al-Qaeda with extensive fighting experience, al-Hazmi and al-Mihdhar were chosen by Osama bin Laden for an ambitious terrorist plot to pilot commercial airliners into designated targets in the United States.

The CIA reportedly received al-Hazmi's name on a list of 19 persons suspected of planning an attack in the near future.

Following the attacks, al-Hazmi's participation was initially dismissed as that of a "muscle hijacker", but he was later revealed to have played a larger role in the operational planning than previously believed.

CNN's preliminary report following the attacks claimed that an unnamed acquaintance relayed '"He told me once that his father had tried to kill him when he was a child.

He never told me why, but he had a long knife scar on his forearm", and claimed that his older brother was a police chief in Jizan.

Known as Rabi'ah al-Makki during the preparations,[6] al-Hazmi had been so eager to participate in operations within the United States, he already had a US visa when bin Laden selected him.

[4] Al-Hazmi obtained a B-1/B-2 tourist visa on April 3, 1999, from the US consulate in Jeddah, Saudi Arabia, using a new passport he acquired a few weeks earlier.

[12] On January 5, al-Hazmi arrived in Kuala Lumpur, where he met up with al-Mihdhar, bin Attash, and Abu Bara.

The group was in Malaysia to meet with Hambali for the 2000 Al Qaeda Summit, during which key details of the attacks may have been arranged.

At this time, there was an East Asia component to the September 11 attacks plot, but bin Laden later canceled it for being too difficult to coordinate with operations in the United States.

[13][14] In Malaysia, the group stayed with Yazid Sufaat, a local member of Jemaah Islamiyah, who provided accommodations at request of Hambali.

Malaysian authorities reported that al-Mihdhar spoke at length with Tawfiq bin Attash, one of the Yemenis, and others who were later involved in the USS Cole bombing.

[15] On 15 January 2000, al-Hazmi and al-Mihdhar arrived together at Los Angeles International Airport from Bangkok, and were admitted for a six-month period.

[7] On February 1, 2000—17 days upon entering the United States—the two men encountered Omar al-Bayoumi and Caysan Bin Don at a halal food restaurant on Venice Boulevard in Culver City.

Instead, the men slept on mattresses on the floor, yet they carried briefcases, were frequently on their mobile phones, and were occasionally picked up by a limousine.

[24] Al-Mihdhar and al-Hazmi raised some suspicion when they offered extra money to their flight instructor, Richard Garza, if he would train them to fly jets.

[29] Al-Mihdhar returned to Yemen, which angered Khalid Sheikh Mohammed, who did not want al-Hazmi to be left alone in California.

[7] In September, al-Hamzi and al-Mihdhar both moved into the house of FBI informant Abdussattar Shaikh, although he did not report the pair as suspicious.

Two days later on 1 April 2001, Oklahoma police officer C. L. Parkins pulled al-Hazmi over for speeding in their Corolla along with an additional citation for failing to use a seatbelt together totaling $138.

A routine inspection of his California drivers license turned up no warrants or alerts, although his name was known to both the NSA and the CIA as a suspected terrorist.

The 9/11 Commission wrote that al-Hazmi and Hanjour met Alrababah at the Dar al Hijra mosque who was a computer technician who had moved from West Paterson, New Jersey and was there to ask imam Anwar al-Awlaki about finding a job.

[36] Police found his telephone number in the contacts of Ramzi bin al-Shibh (the "20th hijacker") when they searched his Hamburg apartment while investigating the 9/11 attacks.

[40] On 30 June, al-Hazmi's car was involved in a minor traffic accident on the east-bound George Washington Bridge.

[7] On 20 July, al-Hazmi and fellow hijacker Hani Hanjour flew to the Montgomery County Airpark in Maryland from on a practice flight from Fairfield, New Jersey.

[3] On 23 August, Israeli Mossad reportedly gave his name to the CIA as one of 19 belonging to US residents who they said were planning to attack the United States in the near future.

[46] He had not been placed on terrorist watch lists, nor did the CIA or NSA alert the FBI, Customs and Immigration, or local police and enforcement agencies.

[51] On 10 September, the day before the September 11 attacks, Hanjour, al-Mihdhar, and al-Hazmi checked into the Marriott Residence Inn in Herndon, Virginia, where Saleh Ibn Abdul Rahman Hussayen, a prominent Saudi government official, was staying – although no evidence was ever uncovered that they had met, or knew of each other's presence.

[58] Nawaf al-Hazmi's 1988 blue Toyota Corolla was found on the next day in Dulles International Airport's hourly parking lot.

Inside the vehicle, authorities found a letter written by Mohamed Atta, maps of Washington, D.C. and New York City, a cashier's check made out to a Phoenix flight school, four drawings of a Boeing 757 cockpit, a box cutter, and a page with notes and phone numbers.

[8] Late in 2005, Army Lt. Col. Kevin Shaffer and Congressman Curt Weldon alleged that the Defense Department data mining project Able Danger had kept Nawaf al-Hazmi, Khalid al-Mihdhar, Mohamed Atta and Marwan al-Shehhi all under surveillance as al-Qaeda agents.