I did not ignore. He said he could not see exactly where it hit. The key is that he did see it go down and 'hit' something. He did not see it fly over and beyond. After it 'hit' something, he did not see it flying around again. From his vantage point at ~3,000 feet agl, he could see very well (nice clear day). I also have 'as it happened' audio for 2 Arlington County police officers on Columbia Pike. The saw it go down and 'hit' something. They did not see it again after that and they were both facing towards the Pentagon.
So here we have a a plane, described 'as it happened' as an American Airlines 757. The 'as it happened' record indicates it 'hit' something, never to be seen again. The radar tells the same story. So, what happened to the plane mudlark?