It's the morning of September 11, 2001 and the flight crew of United 93 -- Captain Jason M. Dahl (JJ JOHNSON), First Officer LeRoy Homer (GARY COMMOCK) and flight attendants Deborah Welsh (POLLY ADAMS), CeeCee Lyles (OPAL ALLADIN), Wanda Anita Green (STARLA BENFORD), Sandra Bradshaw (TRISH GATES) and Lorraine G. Bay (NANCY McDONIEL) -- are preparing for their cross-country flight from Newark to San Francisco.
But little do they or ordinary passengers such as Todd Beamer (DAVID ALAN BASCHE) realize that a number of terrorists are also on the flight. But Ziad Jarrah (KHALID ABDALLA), Saeed Al Ghamdi (LEWIS ALSAMARI), Ahmed Al Haznawi (OMAR BERDOUNI) and Ahmed Al Nami (JAMIE HARDING) don't act right away. Instead and after an unexpected delay, they wait for the right moment, all as their comrades in three other airliners have already commandeered their planes.
All of which initially has FAA national operations manager Ben Sliney (BEN SLINEY) and a host of air traffic controllers around the country perplexed. Since there hasn't been a domestic hijacking in decades, they can't fathom that's what's occurring. But when they can't contact several planes -- that subsequently crash into both towers of the World Trade Center in Manhattan as well as the Pentagon just outside Washington, DC. -- they react to the increasingly frantic situation by trying to get the military and administration to do something.
After taking control of the plane, the terrorists change course and head toward Washington. Initially terrified into submission by the hijackers' violence and threat to blow up the plane, the passengers and flight attendants contact those back on the ground. But when they get word of what's occurring and realize what's likely to happen to them, they decide they must confront the hijackers and try to regain control of their plane.