Actually, it's been confirmed that Elvis was the twentieth pilot. Elvis became a born again Muslim after meeting Mohammed Ali at a prayer breakfast (just wasn't the sort of prayer breakfast The King was expecting). Well, one thing led to another and Elvis, who was already flight trained, met the Osama and in fact wrote a song about it, which Ray Stevens purglarized into "Osama Yo'Mama".

The date 911 was chosen because if you turn it upside down you get 116 which was the number of pounds Elvis was above his ideal weight, although my sources are hazy on whether or not this was a mistake.

One of the web sites that specializes in really gross photos and videos at one time had a picture of Osama in one of those sequined Elvis costumes, although these can be faked.