Ok, you right but fly a Boing with a little knowlenge of civilian aircraft is not easy, but not imposible. My theory if that one of the terrorist use the pilot to make the corrections and when near of the building they take command in the last seconds, enough to aim without loss the overall control and sustentation force.
Damn, they convert it in a guided missile.
"We did it!!!"
>May the force be with you<
Luke Skywalker, 38th Kokou Sentai