The Pentagon's air-defence command missed an opportunity to possibly intercept at least one of the hijacked planes on September 11th, the federal panel reviewing the attacks said today.
A report released by the commission at its final public hearing offered a chilling account of the day America suffered its worst terrorist attack.
It details a series of missteps by aviation and military officials that squandered precious moments between the time air-traffic controllers became aware of the first hijacking and the crash of United Airlines Flight 93 into a Pennsylvania field more than an hour later.
One section of the report includes transcripts of three brief transmissions from the cockpit of American Airlines Flight 11, which took off from Boston and was the first plane to strike the World Trade Center.
A person believed to be Mohamed Atta, the alleged ringleader of the 19 hijackers, who piloted the plane, is heard saying to passengers: "We have some planes. Just stay quiet and you'll be OK. We are returning to the airport."
Later, Atta tells the passengers, "If you try to make any moves, you'll endanger yourself and the airplane."
The report recounted confusion at the Federal Aviation Administration and the North American Aerospace Defence Command (NORAD) that led to delays in scrambling fighter jets to intercept the planes.
Vice President Dick Cheney eventually issued an order to shoot down hijacked planes, but military pilots did not receive it until the last of the four planes - United Airlines Flight 93 - crashed in Pennsylvania after passengers fought back against the hijackers. Mr Cheney said he received the authorisation in an earlier phone call with President Mr George Bush.
The report largely blamed inadequate emergency procedures that contemplated more time to react to a traditional hijacking rather than a suicide hijacking.