i would suggest taken a look at this website, if you don't want the Music with the nice effect go here, there's more then enough evidence here that shows they there was no plane involved
http://www.serendipity.li/wot/pentagon/spencer05.htm

I find this pic below funny, it shows if there was a plane it would have had to go that low at that angel traveling more the 450+MPH (This is off the website)