How a 42-min delay prevented possible plane crash at WH or US Capitol during 9/11?

During 9/11 attacks, a fourth flight with hijackers on board to Washington was delayed by 42 minutes due to traffic. It allowed Flight 93's passengers to receive calls about New York and Pentagon attacks. The alerted passengers stormed hijackers, preventing a possible attack on White House or the Capitol by forcing them to crash the plane in a Pennsylvania field.