Mohamed Atta

He piloted the first plane, American Airlines Flight 11, into the World Trade Center. Investigators say that he was the ringleader of the Sept. 11 plot.

Mohamed Atta was born in Egypt, in a city on the Nile delta named Kafr el Sheikh. Investigators say Atta listed Sept. 1, 1968, as his birthdate. Atta's father, an attorney, was a domineering figure and a strict disciplinarian; his mother doted on him. Atta's siblings, two older sisters, are both successful and educated: one is a medical doctor and the other is a professor of zoology. After Atta was born, his family moved from Kafr el Sheikh to Cairo, where his father still practices law.

Atta's father told The New York Times that his son began praying around 1980, when he was 12 or 13. "He was not ordinary," says the senior Atta. "He was exceptional. He was a gentle person, very shy, unassuming, and highly sensitive."

Atta studied architecture in the Engineering Faculty at Cairo University from 1985 to 1990. As he and his generation reached their early 20s, they were exposed to the angry passions and resentments swirling through Cairo. Egyptians were angry at a ruling elite that was seen as corrupt and undemocratic -- and angry at America for supporting such a regime, and for being Israel's strongest ally.

Atta became a member of an "engineering syndicate," a trade or professional group, after he graduated from Cairo University. The Washington Post reported that Atta's syndicate was an "unofficial base" for the Muslim Brotherhood, an Islamic political organization, where it recruited members and propagated its ideas -- one of which was the demonization of the U.S. for its support of the Egyptian government.

After graduation, Atta worked at a German company in Cairo until he obtained a visa to continue his studies in urban planning in Germany. He enrolled at a technical university near Hamburg in October 1992.

>> See the chronology for details on Atta's life from 1992-2001.

Marwan al-Shehhi

He flew the second plane, United Airlines Flight 175, into the World Trade Center.

Marwan al-Shehhi was born on May 9, 1978, in the United Arab Emirates. Details about al-Shehhi's life in the UAE are difficult to acquire. According to an October 2001 article in the New York Times, "If residents of Mr. Shehhi's hometown had heard of him before now, they were certainly not telling strangers. Four hours spent in the community yielded no address and no one -- policemen, firemen, pedestrians or local officials -- who did anything more than shrug at the mention of his name."

Press reports indicate that al-Shehhi's family lives in a village in Ras al-Khaimah, one of the seven emirates that make up the UAE. Al-Shehhi's father, who is now deceased, reportedly was the muezzin, the person who called the faithful to prayer at the local mosque. In 1997, al-Shehhi left the UAE after a family crisis and moved to Germany, where he first studied German at the University of Bonn before moving to Hamburg, where he enrolled at the same school as Mohamed Atta.

>> For more about how Hamburg was likely a factor in radicalizing al-Shehhi, Atta, and Jarrah, read the Q&A with correspondent Hedrick Smith.

Ziad Jarrah

He piloted United Flight 93 to its fiery crash in Pennsylvania.

Ziad Jarrah was born on May 11, 1975, in Al Marj, a town in Lebanon east of the Bekaa Valley. An only son, Jarrah's father is a civil servant and his mother is a school teacher. Though Jarrah was a Sunni Muslim, his parents sent him to a Catholic school in Beirut. In 1996, a year after he graduated, he left Lebanon for Greifswald, Germany, where he studied German for two semesters before continuing his studies in aviation engineering at the University of Applied Science in Hamburg.

In an interview with the Canadian Broadcasting Corp., Jarrah's uncle, Jamal Jarrah, says, "[Jarrah] was the kind of boy that was raised well and was treated in a very good manner. ... He was a happy boy." When he was young, Jarrah, according to his uncle, espoused none of the extremist beliefs that would become synonymous with the Sept. 11 attacks. "He never cared about politics. ... He was not interested in religion," says Jamal Jarrah. "Twenty-one years, we know Ziad closely. ... He's the person who loves life."

>> See the chronology for details on Jarrah's life from 1996-2001.