Some people suspect he was a Saudi agent and an accessory to the attacks. While Saudi Arabia firmly maintains that al-Bayoumi is not an agent of theirs, the FBI has concluded that he has several links to terrorism.
Al-Bayoumi was probably born around 1959, but virtually nothing is known of al-Bayoumi's early life. Until 1994 he lived in Saudi Arabia, working for the Saudi Ministry of Defense and Aviation, a department headed by Prince Sultan bin Abdul Aziz.
In August 1994, al-Bayoumi moved to the United States and settled down in San Diego, California, where he became involved in the local Muslim community. He was very inquisitive, and was known to always carry around a video camera. According to several sources   (Newsweek 11/22/03, 11/24/03) , al-Bayoumi was strongly suspected by many residents of being a Saudi government spy. The man the FBI considered their "best source" in San Diego said that al-Bayoumi "must be an intelligence officer for Saudi Arabia or another foreign power," according to Newsweek Magazine.
At this time, al-Bayoumi was paid about $3,000 per month by Dallah Avco, a Saudi company closely tied to the Saudi Ministry of Defense and Aviation, al-Bayoumi's former employer. The salary was officially for a project in Saudi Arabia, although he was living in the United States at the time and apparently did no work for them. For five years, the Saudi ministry reimbursed Dallah Avco for al-Bayoumi's salary, and he was considered a civil servant. When the company tried to fire al-Bayoumi in 1999, a Saudi government official replied with a letter marked "extremely urgent" that the government wanted al-Bayoumi's contract renewed "as quickly as possible." Al-Bayoumi was quickly rehired. Dallah Avco is currently[when?] being investigated by the FBI for ties to al-Qaida.
In June 1998, an anonymous Saudi philanthropist donated $500,000 to have a Kurdish mosque built in San Diego, on the condition that al-Bayoumi hired as maintenance manager with a private office. The donation was accepted, but because al-Bayoumi rarely showed up for work, the mosque's leadership became unhappy with him. Eventually, they moved to fire him.
Some time in late 1999 or early 2000, Omar al-Bayoumi began receiving another monthly payment–this one from Princess Haifa bint Faisal, the wife of Bandar bin Sultan, the Saudi ambassador to the U.S. Checks for between $2,000 and $3,000 were sent monthly from the princess, through two or three intermediaries, to al-Bayoumi. The payments continued for several years, totaling between $50,000 and $75,000.
Al-Hazmi and al-Mihdhar
In January 2000, al-Bayoumi drove to Los Angeles, saying he was going "to pick up visitors", according to an FBI source. First, al-Bayoumi visited the Saudi consulate there in LA and had a closed-door meeting with Fahad al Thumairy, according to Newsweek. (After 9/11, al Thumairy was barred entry into the U.S. due to his links to terrorism.) It was only afterward that al-Bayoumi met his visitors.
On January 15, 2000, future 9/11 hijackers Nawaf al-Hazmi and Khalid al-Mihdhar flew to Los Angeles, California from Bangkok, Thailand, just after attending the 2000 Al Qaeda Summit in Kuala Lumpur, Malaysia. The final 9/11 Commission Report noted:
- Hazmi and Mihdhar were ill-prepared for a mission in the United States. . . Neither had spent any substantial time in the West, and neither spoke much, if any, English. It would therefore be plausible that they or [Khalid Sheikh Mohammed] would have tried to identify, in advance, a friendly contact for them in the United States. . . We believe it unlikely that Hazmi and Mihdhar. . . would have come to the United States without arranging to receive assistance from one or more individuals informed in advance of their arrival."
Al-Bayoumi met the hijackers at a restaurant after their landing; he claims he met them by accident. He invited the two hijackers to move to San Diego with him, and they did. Al-Bayoumi found them an apartment, co-signed the lease, and gave them $1500 to help pay for their rent. Al-Bayoumi also helped the two obtain driver's licenses, rides to Social Security, and information on flight schools. Al-Bayoumi says he was being kind to fellow Muslims in need, and had no idea of their plans. But according to Newsweek magazine a former top FBI official, speaking on condition of anonymity, said, "We firmly believed that he had knowledge [of the 9/11 plot], and that his meeting with them that day was more than coincidence."
Al-Hazmi and al-Mihdar's neighbors later reported that the two struck them as quite odd. They had no furniture, they constantly played flight simulator games, and limousines picked them up for short rides in the middle of the night.  During this time, al-Bayoumi lived across the street from them. Throughout this period, the payments from Dallah Avco, his titular employer, greatly increased. Al-Hazmi and al-Mihdar later moved into the house of Abdussattar Shaikh, a friend of al-Bayoumi's, who was secretly working as an FBI informant at the time. 
Arrest and release
In July 2001, Omar al-Bayoumi moved to England to pursue a PhD at Aston University. Ten days after the September 11 attacks he was arrested by British authorities working with the FBI. He was held on an immigration charge while the FBI and Scotland Yard investigated him. His phone calls, bank accounts, and associations were researched, but the FBI says they found no connections to terrorism. He was released, and went back to studying at Aston, and later moved to Saudi Arabia. Anonymous British officials suggest al-Bayoumi must have been protected by the FBI, because "giving financial aid to terrorists is a very serious offense and there is no way [the FBI] would have let him go scot-free."
The issue was reopened when the potential links between al-Bayoumi and the Saudi Embassy were reported in the press. Under pressure from Congress, the FBI re-examined the case. They concluded that the allegations were "without merit," and they "abandoned further investigation." But contemporary news accounts reported that "countless intelligence leads that might help solve [the case] appear to have been under investigated or completely overlooked by the FBI."
The final 9/11 Commission reports stated "we have seen no credible evidence that he believed in violent extremism, or knowingly aided extremist groups."