Atta disappeared from Germany for periods of time, embarking on the hajj in 1995 but also meeting Osama bin Laden and other top al-Qaeda leaders in Afghanistan from late 1999 to early 2000.

Atta returned to Hamburg in February 2000 and began inquiring about flight training in the United States, where he, Jarrah, and al-Shehhi arrived in June to learn how to pilot planes, obtaining instrument ratings in November.

[2] Mohamed Atta was born on 1 September 1968, in Kafr el-Sheikh, located in the Nile Delta region of Egypt (then a part of the United Arab Republic).

The couple explained at dinner that they ran an exchange program and invited Atta to continue his studies in Germany; they also offered him room and board at their home in the city.

Atta began adhering to the strictest Islamic diet, frequenting the most conservative mosques, socializing seldom, and acting disdainfully towards the couple's unmarried daughter who had a young child.

[24] Atta had harbored a desire to return to his native city ever since he finished his studies in Hamburg, but he was prevented by the dearth of job prospects in Cairo, his family lacking the "right connections" to avail the customary nepotism.

[32] These beliefs were even stronger during Operation Infinite Reach, as he believed that Monica Lewinsky was a Jewish agent influencing American president Bill Clinton against aiding Palestine, which would later play a key role in creating the Hamburg cell.

[24] In Hamburg, Atta was intensely drawn to al-Quds Mosque which adhered to a "harsh, uncompromisingly fundamentalist, and resoundingly militant" version of Sunni Islam.

[3][38] This was the same day that Israel, much to Atta's fury, attacked Lebanon in Operation Grapes of Wrath; signing the will "offering his life" was his response.

[32] The instructions in his last will and testament reflect both Sunni funeral practices along with some more puritanical demands from Salafism, including asking people not "to weep and cry" and to generally refrain from showing emotion.

In late 1999, Atta, Shehhi, Jarrah, Bahaji, and bin al-Shibh decided to travel to Chechnya to fight against the Russians, but were convinced by Khalid al-Masri and Mohamedou Ould Salahi at the last minute to change their plans.

[48][additional citation(s) needed] German investigators said that they had evidence that Mohamed Atta trained at al-Qaeda camps in Afghanistan from late 1999 to early 2000.

[57][58] On 6 June 2002, ABC's World News Tonight broadcast an interview with Johnelle Bryant, former loan officer at the U.S. Department of Agriculture in south Florida, who told about her encounter with Mohamed Atta.

On 26 December, Atta and Shehhi needed a tow for their rented Piper Cherokee on a taxiway of Miami International Airport after the engine shut down.

[67] On 27 June, Atta flew from Fort Lauderdale to Boston, Massachusetts, where he spent a day, and then continued to San Francisco for a short time, and from there to Las Vegas.

[72] The absence of other hotel stays, signed receipts or credit card stubs has led investigators to believe that the men may have met in a safe house provided by other al-Qaeda operatives in Spain.

[10] On 4 August, Atta is believed to have been at Orlando International Airport waiting to pick up suspected "20th Hijacker" Mohammed al-Qahtani from Dubai, who ended up being held by immigration as "suspicious."

The same day, he booked a one-way first-class ticket via the Internet on America West Flight 244 from Ronald Reagan Washington National Airport to Las Vegas.

[81] On 10 September 2001, Atta picked up al-Omari from the Milner Hotel in Boston, Massachusetts, and the two drove their rented Nissan Altima to a Comfort Inn in South Portland, Maine.

[90]: 38  On the phone with American Airlines after the hijackers had assumed control of the plane, flight attendant Betty Ong reported that the cockpit was unresponsive and inaccessible.

Evidently, he tried to deliver a message over the cabin's PA system instructing the passengers and crew to stay put, but pressed the wrong switch and thereby tipped off ATC that the flight had been hijacked.

He held interviews with the German news magazine Bild am Sonntag in late 2002, saying his son was alive and hiding in fear for his life, and that American Christians were responsible for the attacks.

[102] Mahmoud Atta, a naturalized U.S. citizen, was subsequently deported from Venezuela to the United States, extradited to Israel, tried, convicted, and sentenced to life in prison.

[103] After the attacks, there were also reports stating that Mohamed Atta had attended the International Officers School at Maxwell Air Force Base in Montgomery, Alabama.

The Washington Post quoted a United States Air Force official who explained, "discrepancies in their biographical data, such as birth dates 20 years off, indicate we are probably not talking about the same people.

"[104] In the months following the 11 September attacks, officials at the Czech Interior Ministry asserted that Atta made a trip to Prague on 8 April 2001, to meet with an Iraqi intelligence agent named Ahmed Khalil Ibrahim Samir al-Ani.

[106][107][108] In 2005, Army Lt. Col. Anthony Shaffer and Congressman Curt Weldon alleged that the Defense Department data mining project, Able Danger, produced a chart that identified Atta, along with Nawaf al-Hazmi, Khalid al-Mihdhar, and Marwan al-Shehhi, as members of a Brooklyn-based al-Qaeda cell in early 2000.

Phillpott said that Shaffer was "relying on my recollection 100 percent," and the Defense Department Inspector General's report indicated that Philpott "may have exaggerated knowing Atta's identity because he supported using Able Danger's techniques to fight terrorism.

Political psychologist Jerrold Post has suggested that Atta and his fellow hijackers were just following orders from al-Qaeda leadership, "and whatever their destructive, charismatic leader Osama bin Laden said was the right thing to do for the sake of the cause was what they would do.

[117][page needed] On 1 October 2006, The Sunday Times released a video it had obtained "through a previously tested channel", purporting to show Mohamed Atta and Ziad Jarrah recording a martyrdom message at a training camp in Afghanistan.