The commission investigating the Sept. 11 terror attacks holds its final hearings Wednesday and Thursday, with plans to cover the plot carried out by the 19 hijackers and the emergency response by the Federal Aviation Administration and U.S. air defenses.

Panel members say they will delve into the actions of the nation's top leaders during critical moments of the attacks. Among the expected findings: The nation's air defense was woefully outdated, focused more on intercepting Soviet bombers than hijacked airliners.

The hijackers might have planned a strike date for months earlier but delayed it, giving U.S. authorities a last chance to detect the plot. Confusion and miscommunication among agencies reigned during the attacks, hindering a response.

"We're going to talk about the evolution of Al Qaeda and how they moved from one type of organization in the late 1980s to a more fast-acting, poisonous organization in the 1990s, more spread out and dispersed," said Timothy Roemer (search), a Democratic commissioner and former representative from Indiana.

"We'll be looking at the timeline as to whether or not we had an opportunity to deflect any of the airliners, and how decisions were made by the highest people in government," he said.

Scheduled to testify Wednesday are field agents from the FBI and CIA, as well as Patrick Fitzgerald (search), a former attorney in New York who prosecuted alleged terrorists in the 1993 bombing of the World Trade Center and the 1998 bombings of two U.S. embassies in Africa.

Missing from Wednesday's schedule is German prosecutor Matthias Krauss (search), who canceled at the last minute. Krauss, who investigated the Al Qaeda cell in Hamburg, Germany, had been expected to highlight problems with U.S. intelligence-sharing.

On Thursday, the 10-member panel will hear from Air Force Gen. Richard Myers, chairman of the Joint Chiefs of Staff, as well as officials from the FAA and the North American Aerospace Defense Command (search). They will discuss whether a military response could have limited the Sept. 11 destruction by shooting down the airliners.

Officials have acknowledged the fighters did not get airborne as quickly as possible. NORAD and FAA officials say that since Sept. 11 they have established new chains of communication and increased the number of warplanes on alert.

The commission, facing a July 26 deadline for a final report, is winding down its 1½-year investigation after interviewing more than 1,000 witnesses, including President Bush, and reviewing more than 2 million documents.

Several commissioners have told The Associated Press that drafts of the final report detail the many communication gaps and missteps by FBI and intelligence officials in detecting the plot. But they said the drafts refrain from placing blame on individuals in the Bush and Clinton administrations to avoid charges of partisanship.

That troubles some relatives of Sept. 11 victims, still seeking closure nearly three years after the attacks. They sent a letter to commissioners this week asking for tough questioning and accountability in the final hearing, saying the truth should come before politics.

Nearly three years after the attacks, Lorie Van Auken is still waiting to learn why her husband had to die — and counting on the commission's last hearing into the hijacking plot to finally provide some answers.

"Nineteen men defeated us with not a lot of money and killed 3,000 people. That's not a success story," said Van Auken, of East Brunswick, N.J., who believes the Sept. 11 commission has been too soft on government witnesses in its 11 previous hearings. Her husband, Kenneth, died in the World Trade Center collapse.

"What happened on that day? What did the president know?" she asked. "When everything went wrong, we don't need to hear commissioners telling witnesses they did a great job."

"We're going in with our hearts in our mouths," said Mindy Kleinberg, whose husband, Alan, was killed in the World Trade Center collapse. "You pray. You know it's going to be emotional. We just hope on top of the emotion, we don't leave frustrated again."

Kristen Breitweiser of Middletown Township, N.J., whose husband, Ronald, died in the World Trade Center, said a lack of foresight on the part of those agencies was compounded by officials' mistakes on the morning of Sept. 11.

"I think we were ill-prepared, and I think people showed poor judgment," Breitweiser said. The plane that crashed into the Pentagon, in particular, could have been stopped, she contended.

Both NORAD and FAA officials say changes have been implemented since the attacks. They have established chains of communication. Generals — rather than just the president — have been given authority to order the fighter pilots to shoot down hijacked aircraft. The number of warplanes on alert has been increased, and fighters are put on patrol over U.S. cities and events deemed possible terrorist targets.

When the Sept. 11 terrorists struck, the United States and Canada were defended by 20 fighter aircraft, arrayed in pairs in 10 locations, said Lt. Col. Roberto Garza, a NORAD spokesman. They were kept armed and fueled, with pilots nearby, ready to take off in less than 15 minutes.

They were a remnant of the Cold War, when North America worried more about intercepting Soviet bombers than hijacked airliners. On Sept. 11, their focus was directed outward, toward threats that might approach American coastlines. Potential hijackings were the domain of law enforcement.

The only fighters that were close to the attacks were in Massachusetts and Virginia.

The best information about the sequence of events on Sept. 11 comes from a timeline provided by NORAD in the months after the attacks. NORAD spokesman Garza said some aspects of the timeline now are considered inaccurate, however, but he refused to be more specific.

The two Boston flights that hit the World Trade Center, American Airlines Flight 11 and United Airlines Flight 175, were the first to take off and the first to be hijacked.

When two NORAD F-15 Eagle fighters rocketed into the sky from Otis Air National Guard Base, Mass., Flight 11 had already hit the North Tower, and the fighters were 10 minutes away when Flight 175 struck the South Tower.

The FAA and NORAD had a better chance of stopping American Airlines Flight 77, which had broken from its flight path just before 9 a.m., relatives of the victims say. The government had 45 minutes until the plane would hit the Pentagon.

By then, American skies were in chaos. At one point, the FAA was tracking 11 planes that it feared could have been hijacked, said Laura Brown, a spokeswoman for the agency. Air Force fighters were taking off from bases unarmed, and someone floated the idea of using one of them to ram a hijacked airliner.

Still, two events would have been required for the Pentagon strike to have been averted.

First, President Bush would have had to have ordered that any hijacked airliners be shot down. Bush ultimately did make that call, but only after the Pentagon was hit.

Second, NORAD's F-16 Fighting Falcons at Langley Air Force Base, near Norfolk, Va., would have had to have been launched sooner.

Why they weren't is unclear.