In an unflinching report, the panel depicted the Federal Aviation Administration as slow to alert the military to the hijackings — even failing to pass along word that one of the planes had been seized.
Chilling radio transmissions by the Sept. 11 hijackers from the planes they commandeered were played publicly for the first time Thursday, providing a vivid and horrifying portrait as they unfolded on that fateful day before confused air traffic officials and military personnel.
"We have some planes. Just stay quiet and you'll be okay. We are returning to the airport. Nobody move. Everything will be okay. Just stay quiet," Atta is heard saying on tape.
On the final day of testimony before the Sept. 11 Commission, those words were portrayed as launching a chaotic scramble in the U.S. government to determine both what was going on and how to stop it.
But in the end, the commission concluded, both the FAA and the military were "unsuited in every respect" to prevent what happened that day.
In testimony before the panel, Gen. Ralph Eberhart said military pilots would have been able to "shoot down the airplanes" if word of had been immediate. The commission, though, made no such claim.
Some military pilots "were never briefed about the reason they were scrambled," the panel said. The Secret Service, worried about a plane approaching the capital, went "outside the chain of command" to ask for warplanes to be sent aloft.
President Bush, in Florida when the terrorists struck, was not immune to communications woes. The commander in chief later told interviewers he had been frustrated that day at delays in establishing secure phone links with officials in a capital city feared under attack.
"There was a real problem with communications that morning," the commission's chairman, former New Jersey Gov. Thomas Kean, told reporters. "There were a lot of people who should have been in the loop who were not in the loop."
The commission sketched its picture as it neared the end of an exhaustive investigation into terrorist attacks that killed nearly 3,000. Terrorists seized four planes on a single day, flying two of them into the World Trade Center and one into the Pentagon.
The fourth, headed for Washington, D.C., crashed in the Pennsylvania countryside after passengers struggled with their hijackers.
"The nation owes a debt to the passengers. ... Their actions saved the lives of countless others and may have saved either the U.S. Capitol or the White House from destruction," the commission's report said.
It noted that officials at NORAD — the North American Aerospace Defense Command — maintain they could have intercepted and shot down the plane, United Flight 93. "We are not sure," the commission said.
Eberhart, the NORAD commander, made an even bolder claim as he testified before the panel. He said all four planes could have been shot from the sky if the FAA had informed the military as soon as it knew of each hijacking.
"If that is the case, yes, we could shoot down the airplanes," he said.
It was a claim the panel steered clear of making, and none of the commissioners responded when he made it.
As is its custom, the commission had its staff report read aloud, a recitation spiced by snippets of taped audio conversations that most Americans were hearing for the first time.
"We have some planes. Just stay quiet and you'll be O.K. We are returning to the airport," says one voice, believed to belong to Mohamed Atta, the alleged ringleader of 19 hijackers.
Those few chilling words, heard at the FAA's Boston Center, were the first the government knew of any of the hijackings.
Moments later, there was more. "Nobody move. Everything will be OK. If you try to make any moves, you'll endanger yourself and the airplane. Just stay quiet."
On the ground, there was skepticism bordering on disbelief. "Is this real-world or exercise?" an unidentified NORAD official said when told by the FAA there was a need to send F-16 fighter planes aloft.
"No, this is not an exercise, not a test," came back the reply.
In a tunnel beneath the White House, Cheney talked later to the president. The vice president subsequently told commissioners Bush had authorized orders for military pilots to shoot down hijacked aircraft that refused to follow orders.
Cheney issued the orders on several occasion, the report said, unaware that the last of the four hijacked planes — heading for Washington — had already crashed in Pennsylvania.
A half hour later, Cheney erroneously told Defense Secretary Donald Rumsfeld he believed military pilots had "already taken a couple of aircraft out."
Adding to the woes were reports of additional terrorist activities.
"We fought many phantoms that day," testified Gen. Richard Myers, chairman of the Joint Chiefs of Staff. He noted that reports of car bombings and other terrorist acts spread quickly — and falsely.
About a half hour after the last of the four seized planes crashed came word of another intruder aloft. "Eventually, the shelter received word that the alleged hijackers five miles away had been a Medevac helicopter," the report said.
"The frontline civilian and military agencies struggled to "improvise a homeland defense against an unprecedented challenge they had never encountered and had never trained to meet," the panel said.
Whatever the problems, the panel praised the actions of government personnel forced to make split-second decisions. Air traffic controllers brought nearly 4,500 planes safely to the ground, for example, juggling many more aircraft than usual once the skies were ordered cleared.
The commission held its final day of public hearings as Bush challenged its day-old finding that there had been no "collaborative relationship" between Saddam Hussein and the al Qaeda terrorists responsible for the attacks.
"There was a relationship between Iraq and al Qaeda," Bush insisted. "This administration never said that the 9/11 attacks were orchestrated between Saddam and al Qaeda."
"We did say there were numerous contacts between Saddam Hussein and al Qaeda, for example, Iraqi intelligence agents met with (Osama) bin Laden, the head of al Qaeda in the Sudan."
The commission had investigated the meeting, and said it did not indicate the terrorists and Iraqi president were forging ties.
The difference is potentially a significant one, since Bush and top administration officials cited ties between al Qaeda and Saddam in the run-up to the invasion of Iraq in 2003.
Neither Kean, nor former Democratic Rep. Lee Hamilton, the commission's vice chairman, showed any inclination for a public spat with Bush on the issue.
Hamilton said, "The sharp differences that the press has drawn .... are not that apparent to me."