I've researched the the terrorist attack on 11-Sep-2001 fairly extensively, though i haven't written much about it other than brief references. Why i haven't written more about it, i don't know. Perhaps because it's such an incredibly complex, convoluted subject that's full of misinformation and disinformation. One of the facts that many so-called 'researchers' choose to ignore is the role played by Israel and its intelligence arm, the Mossad. Indeed the fingerprints of the Israelis are all over 9/11. Even Fox 'News' aired a special regarding a potential connection, though it aired only once and was subsequently scrubbed from their website.
One of the most well known connections between Israel and the 9/11 attack is the so-called 'Dancing Israelis' who witnesses said appeared to be celebrating the event while photographing themselves against the backdrop of the burning towers. They worked for a company called Urban Moving Systems which appears to have been a Mossad front. Apparently the FBI has 76 photographs captured by the Israelis in their possession, however they only released a few redacted images as a result of a FOIA request. You can view here.