POD 1: The President does not go to Florida, and is in the White House on 9/11.
POD 2: Donald Rumsfeld, who in OTL was in a meeting at the Pentagon when the plane hits, is forced to move the meeting to another room within the Pentagon.
POD 3: The brave souls of Flight 93 fail to stop the plane from reaching Washington.
Result: Flight 93 hits the White House, and Vice-President Dick Cheny, National Security Advisor Condoleezza Rice and President George W. Bush are killed. When Flight 77 hits the Pentagon, Secretary of Defence Donald Rumsefeld is killed.
Now, Speaker of the House of Representatives Dennis Hastert is President. How does he handle the attack? Who does he pick to replace Cheny, Rice and Rumsfeld? How will history be changed?