Hanjour first went to the United States in 1991, enrolling at the University of Arizona, where he studied English for a few months before returning to Saudi Arabia early the next year.

During his youth, Hanjour wanted to drop out of school to become a flight attendant, although his brother Abdulrahman discouraged this route, and tried to help him focus on his studies.

Hanjour shared a three-bedroom home on the corner of 4th Avenue and 4th Street owned and managed by a father-son team, who made a living renovating and renting rooms to international students and devoting their energies to spreading a born-again Christian influence; Bob, the oldest son, lived in this house and rented the room directly to Hanjour.

Hanjour was a model housemate; he was extremely respectful of others, apolitical in his points of view, and appeared as a nonchalant happy-go-lucky teenager with very weak English-speaking skills.

As early as Hanjour moved into this house, he was under the constant watch of two "uncles" who would pick him up for the weekends so that he would spend time with them within their circle, thereby minimizing his contact with his American housemates and friends from the university.

In December 1991 Hanjour informed Bob that he missed Saudi Arabia and would be leaving the United States due to homesickness.

[8] In April 1996, Hanjour returned to the United States, staying with family friends, Susan and Adnan Khalil, in Miramar, Florida, for a month before heading to Oakland, California, to study English and attend flight school.

[9][10] Hanjour completed the English program in August, and in early September 1996, he attended a single day of ground school courses at the Sierra Academy of Aeronautics before withdrawing, citing financial worries about the $35,000 cost.

Hanjour left Oakland in September and moved to Phoenix, Arizona, paying $4,800 for lessons at CRM Flight Cockpit Resource Management in Scottsdale.

[11] Hanjour re-entered the United States on 15 November 1997,[2] taking additional English courses in Florida, then returning to Phoenix, where he shared an apartment with Bandar al-Hazmi.

[8] After arriving in Florida in November 1997, Hanjour met a man Rayed Mohammed Abdullah Ali, a mutual friend through Bandar al-Hazmi.

His brother, Yasser, relayed that Hanjour, frustrated, "turned his attention toward religious texts and cassette tapes of militant Islamic preachers.

In May 2000, a third person accompanied Nawaf al-Hazmi and Khalid al-Mihdhar to Sorbi's Flying Club where he waited on the ground as they took a flight lesson.

In September Hanjour again sent his $110 registration to the ELS Language Center, which leased space on Holy Names College campus in Oakland, California, to continue his English studies.

On 8 December, Hanjour was recorded flying into the Cincinnati/Northern Kentucky International Airport, and is thought to have met with Nawaf al-Hazmi in San Diego shortly thereafter.

Hanjour came back to San Diego in December 2000, frequently visiting Abdussattar Shaikh's house, which was shared with Nawaf al-Hazmi and Khalid al-Mihdhar.

During this time Hanjour may have visited the San Diego Zoo in February, as a security guard recalls having to page his name to reclaim a lost briefcase containing cash and Arabic documents and later recognized his photograph.

However, in January 2001, Arizona JetTech flight school managers reported him to the FAA at least five times because his English was inadequate for the commercial pilot certificate he had already obtained.

On 4 April 2001, Hanjour asked to forward his utility deposits to 3159 Row Street, Falls Church, Virginia, which was the same address as the mosque.

During his time in New Jersey, he and Hazmi rented three different cars including a sedan in June that Hanjour cosigned with the alias "Hani Saleh Hassan".

Hanjour, along with at least five other future hijackers, are believed to have traveled to Las Vegas several times in mid-2001, where they allegedly drank alcohol, gambled, and visited lap dancing clubs.

[26] On 20 July, Hanjour flew to the Montgomery County Airpark in Maryland from New Jersey on a practice flight with fellow hijacker Nawaf Alhazmi.

[27][28] On 1 August, Hanjour and Almihdhar returned to Falls Church to obtain fraudulent documentation at a 7-Eleven convenience store where an illegal side business operated for such a service.

They drove together to a DMV office at a mall in nearby Springfield, Virginia, where Martinez-Flores gave them a false address in Falls Church to use, and signed legal forms attesting that they lived there.

Their credit card failed to authorize, and after being told the agency did not accept personal checks, the pair left to withdraw cash.

[30] Hanjour began making cross-country flights in August to test security, and tried to rent a plane from Freeway Airport in Maryland; though he was declined after exhibiting difficulty controlling and landing a single-engine Cessna 172.

On 10 September 2001, Hanjour, Mihdhar, and Hazmi checked into the Marriott Residence Inn in Herndon, Virginia where Saleh Ibn Abdul Rahman Hussayen, a prominent Saudi government official, was staying.

[36] In the security tape footage released in 2004, Hanjour appears to walk through the metal detector without setting it off, which likely means that agents at the terminal were not looking at any warning signal that indicated if he had weapons.