Where was united Flight 93 believed to have been headed and why did it not reach that place?

It is believed that the terrorists wanted to drive the plane into either The White House or Congress. Their plans were interrupted by the passengers who gave their lives in a "Hail Mary" effort to take over the airplane, which was successful. The passengers learned of the World Trade Centers falling from calls from their families. Many people called home to tell their loved ones what they were going to do and to say good by. Some had to leave a message which their families found when they returned home from work that day. They caused the plane, flight 34, to come down an uninhabited area outside of Shanksville Pa. Today they are considered heroes for their self-less act.