Terror works like a musical composition， so many instruments， all in tune， playing perfectly together to create their desired effect. It was ， of course， a perfect day 70 deg and flawless skies， perfect for a nervous pilot who has stolen a huge jet and intends to turn it into a missile. It was a Boeing 767 from Boston， American Airlines Flight 11 bound for Los Angeles with 81 passengers， that first got the attention of air traffic controllers. The plane took off at 7：59 a.m. and headed west， over the Adirondacks， before taking a sudden turn south and diving down toward the heart of New York City. Meanwhile American Flight 757 had left Dulles； United Flight 175 left Boston at 7：58， and United Flight 93 left Newark three minutes later， bound for San Francisco. All climbed into beautiful clear skies， all four planes on transcontinental flights， plump with fuel， ripe to explode. "They couldn‘t carry anything-other than an atom bomb-that could be as bad as what they were flying，" observed a veteran investigator.