It has taken me a while to research this topic after HowardRoark2's post. It can't be answered here. If you're willing to keep an open mind then there is plenty of reading which will only make you want to read more. A good start is the 911 Commision Report followed by, or read in conjunction with, David Ray Griffin's book, The 9/11 Commission Report: Omissions and Distortions. When someone posts a 'conspiracy theory' reply you may consider checking out this;
http://www.911truth.org/article.php?...50116064744556
Remember: KIP