When Atta arrived in Germany, he appeared religious, but not fanatically so. This would change, especially as his tendency to assert leadership became increasingly pronounced. According to Binalshibh, as early as 1995 Atta sought to organize a Muslim student association in Hamburg. In the fall of 1997, he joined a working group at the Quds mosque in Hamburg, a group designed to bridge the gap between Muslims and Christians. Atta proved a poor bridge, however, because of his abrasive and increasingly dogmatic personality. But among those who shared his beliefs, Atta stood out as a decisionmaker. Atta's friends during this period remember him as charismatic, intelligent, and persuasive, albeit intolerant of dissent.⁶⁵

In his interactions with other students, Atta voiced virulently anti-Semitic and anti-American opinions, ranging from condemnations of what he described as a global Jewish movement centered in New York City that supposedly controlled the financial world and the media, to polemics against governments of the Arab world. To him, Saddam Hussein was an American stooge set up to give Washington an excuse to intervene in the Middle East. Within his circle, Atta advocated violent jihad. He reportedly asked one individual close to the group if he was "ready to fight for [his] belief" and dismissed him as too weak for jihad when the person declined. On a visit home to Egypt in 1998, Atta met one of his college friends. According to this friend, Atta had changed a great deal, had grown a beard, and had "obviously adopted fundamentalism" by that time.⁶⁶