In particular, the report by the National Commission on Terrorist Attacks Upon the United States -- better known as the 9/11 Commission -- cited poor information issued to the military by the Federal Aviation Administration (FAA), the country's chief civil-aviation agency, which oversees commercial air travel.
As a result, it said, military fighter jets were not alerted in time to shoot down the four hijacked commercial jetliners. Three of the planes hit their targets -- the two towers of New York's World Trade Center, and the Pentagon in Washington. The fourth crashed in a rural area, apparently brought down by passengers who overpowered the hijackers.
The report was issued as the commission was holding the second phase of its 12th and final public hearing. Today's session focused on the U.S. government response to the attacks, which killed roughly 3,000 people.
Opening this session of the hearing were readings from the reports by two staff members. One was Philip Zelikow, who cited not only inept coordination between the civil and military-aviation authorities but also poor communication within the military on how to defend against hijacked airliners that were to be used as missiles.
Shortly after the initial attacks, Vice President Dick Cheney had presidential authority because President George W. Bush was, for his safety, taking a circuitous route back to Washington from a speaking engagement in Florida.
Zelikow said Cheney had given the order that military jet fighters were to shoot down any aircraft that had been hijacked. A plane was assumed to have been hijacked if its pilot ignored military orders to land. Military jet fighters from Langley Air Force Base near Washington were deployed over New York and Washington to protect them.
But Zelikow said the military commander for the northeastern region of the United States did not relay that order to these pilots because "he was unaware of its ramifications."
"In short, while leaders in Washington believed the [military jet] fighters circling above them had been instructed to, quote, 'take out,' end quote, hostile aircraft, the only orders actually conveyed to the Langley pilots were to, quote, 'ID, type, and tail [identify and follow],' end quote."
Later, General Richard Myers, the chairman of the U.S. Joint Chiefs of Staff, testified that some of the confusion could be attributed to policy, not just poor coordination.
Myers said the U.S. military's role has long been to protect the country from attacks emanating from outside its borders, not within. And yet, when the men and women under his command had to adapt to this new threat, he said, they responded well.
"Our military posture on 9-11 [11 September] -- by law, by policy, and in practice -- was focused on responding to external threats, threats originating outside of our borders. Nevertheless, we executed the Continuity of Government plan very well on 9-11, and our servicemen and -women displayed superb professionalism, judgment, and flexibility at every level that day, and I am very proud of their performance," Myers said.
This statement was not good enough for one member of the commission, John Lehman. He is a longtime member of the U.S. Navy Reserve and served for nearly seven years as secretary of the Navy under President Ronald Reagan in the 1980s.
Lehman recalled that in the 1990s, after the collapse of the Soviet Union, the U.S. air defense was carefully scrutinized to make it suitable for the post-Cold War era.
At the time, Lehman said, there was some consideration of eliminating the North American Defense Command (NORAD), which was created to protect the United States from a Soviet airborne attack.
The U.S. government decided to keep NORAD, at least in part to protect the country from a less conventional attack. And yet, Lehman said, problems -- or "glitches," as he called them -- hampered U.S. air defenses on 11 September.
"The glitches in command and control glitches that had really nothing to do with the fact that it was an internal rather than an external [attack], because in the justification for maintaining NORAD, of course, the possibility of intercepting hijacked airliners was part of the justification from the beginning, although the expectation was that they would be foreign airliners, hijacked and incoming," Lehman said.
The commission has been investigating the 11 September attacks for a year and a half. It has interviewed more than 1,000 witnesses -- including Bush and Cheney -- and studied more than 2 million documents. It is expected to issue its final report in July.