In 1996, Khalid Sheikh Mohammed, a Kuwait-born Islamic extremist and influential member of al-Qaida, pitches an idea for an attack on America to bin Laden. He proposes hijacking 10 commercial airplanes and guiding them into targets around the country. Bin Laden likes the idea. In 1998 or 1999, he gives Mohammed the go-ahead to begin planning and provides strategies, as well as funding, for Mohammed's tactical and operational expertise. He also scales back Mohammed's aspirations by limiting the attack to just four planes, believing that 10 would make the plan overly complicated and more likely to fail. Al-Qaida leaders begin screening recruits for their readiness to infiltrate the United States. They carefully select men who could potentially fly -- or train to fly -- commercial aircraft.