Hearing the taped voice of a courageous flight attendant as she calmly narrated the doomed course of American Airlines Flight 11 brought it all back. The frozen horror of that September morning two and a half years ago. The unanswered questions. Betty Ong narrated that first hijacking right up to the moment that Mohamed Atta drove the Boeing 767 into the north tower of the World Trade Center.

Twenty-three minutes into her blow-by-blow account, Ong’s voice abruptly ceased. “What’s going on, Betty?” asked her ground contact, Nydia Gonzalez. “Betty, talk to me. I think we might have lost her.”

Emotional catharsis, yes. There was scarcely a dry eye in the Senate hearing room where 10 commissioners are probing the myriad failures of our nation’s defenses and response to the terrorist attacks of 9/11. But answers? Not many. The most shocking evidence remains hidden in plain sight.

The politically divided 9/11 commission was able to agree on a public airing of four and a half minutes from the Betty Ong tape, which the American public and most of the victims’ families heard for the first time on the evening news of Jan. 27. But commissioners were unaware of the crucial information given in an even more revealing phone call, made by another heroic flight attendant on the same plane, Madeline (Amy) Sweeney. They were unaware because their chief of staff, Philip Zelikow, chooses which evidence and witnesses to bring to their attention. Mr. Zelikow, as a former adviser to the pre-9/11 Bush administration, has a blatant conflict.

“My wife’s call was the first specific information the airline and the government got that day,” said Mike Sweeney, the widowed husband of Amy Sweeney, who went face to face with the hijackers on Flight 11. She gave seat locations and physical descriptions of the hijackers, which allowed officials to identify them as Middle Eastern men-by name-even before the first crash. She gave officials key clues to the fact that this was not a traditional hijacking. And she gave the first and only eyewitness account of a bomb on board.

“How do you know it’s a bomb?” asked her phone contact.

“Because the hijackers showed me a bomb,” Sweeney said, describing its yellow and red wires.

Sweeney’s first call from the plane was at 7:11 a.m. on Sept. 11-the only call in which she displayed emotional upset. Flight 11 was delayed, and she seized the few moments to call home in hopes of talking to her 5-year-old daughter, Anna, to say how sorry she was not to be there to put her on the bus to kindergarten. Ms. Sweeney’s son Jack had been born several months premature, and she had taken the maximum time off over the previous summer to be with her children. “But she had to go back that fall, to hold the Boston-to-L.A. trip,” explained her husband.

American’s Flight 11 took off from Logan Airport in Boston at 7:59 a.m. By 8:14 a.m., the F.A.A. controller following that flight from a facility in Nashua, N.H., already knew it was missing; its transponder had been turned off, and the controller couldn’t get a response from the pilots. The air-traffic controller contacted the pilot of United Airlines Flight 175, which at 8:14 also left Boston’s Logan bound for California, and asked for his help in locating Flight 11.

Sweeney slid into a passenger seat in the next-to-last row of coach and used an Airfone to call American Airlines Flight Service at Boston’s Logan airport. “This is Amy Sweeney,” she reported. “I’m on Flight 11-this plane has been hijacked.” She was disconnected. She called back: “Listen to me, and listen to me very carefully.” Within seconds, her befuddled respondent was replaced by a voice she knew.

“Amy, this is Michael Woodward.” The American Airlines flight service manager had been friends with Sweeney for a decade, so he didn’t have to waste any time verifying that this wasn’t a hoax. “Michael, this plane has been hijacked,” Ms. Sweeney repeated. Calmly, she gave him the seat locations of three of the hijackers: 9D, 9G and 10B. She said they were all of Middle Eastern descent, and one spoke English very well.

Mr. Woodward ordered a colleague to punch up those seat locations on the computer. At least 20 minutes before the plane crashed, the airline had the names, addresses, phone numbers and credit cards of three of the five hijackers. They knew that 9G was Abdulaziz al-Omari, 10B was Satam al-Suqami, and 9D was Mohamed Atta-the ringleader of the 9/11 terrorists.

“The nightmare began before the first plane crashed,” said Mike Sweeney, “because once my wife gave the seat numbers of the hijackers and Michael Woodward pulled up the passenger information, Mohamed Atta’s name was out there. They had to know what they were up against.”

Mr. Woodward was simultaneously passing on Sweeney’s information to American’s headquarters in Dallas–Fort Worth. There was no taping facility in his office, because the most acute emergency normally fielded by a flight service manager would be a call from a crew member faced with 12 passengers in first class and only eight meals. So Mr. Woodward was furiously taking notes.

Amy Sweeney’s account alerted the airline that something extraordinary was occurring. She told Mr. Woodward she didn’t believe the pilots were flying the plane any longer. She couldn’t contact the cockpit. Sweeney may have ventured forward to business class, because she relayed the alarming news to Betty Ong, who was sitting in the rear jump-seat. In professional lingo, she said: “Our No. 1 has been stabbed,” referring to a violent attack on the plane’s purser, “also No. 5,” another flight attendant. She also reported that the passenger in 9B had had his throat slit by the hijacker sitting behind him and appeared to be dead. Betty Ong relayed this information to Nydia Gonzalez, a reservations manager in North Carolina, who simultaneously held another phone to her ear with an open line to American Airlines official Craig Marquis at the company’s Dallas headquarters.

The fact that the hijackers initiated their takeover by killing a passenger and stabbing two crew members had to be the first tip-off that this was anything but a standard hijacking. “I don’t recall any flight crew or passenger being harmed during a hijacking in the course of my career,” said Peg Ogonowski, a senior flight attendant who has flown with American for 28 years.

Betty Ong and Amy Sweeney also reported that the hijackers had used mace or pepper spray and that passengers in business class were unable to breathe. Another dazzling clue to the hijackers’ having a unique and violent intent came in Betty Ong’s earliest report: “The cockpit is not answering their phone. We can’t get into the cockpit. We don’t know who’s up there.”

A male colleague of Ms. Gonzalez then comes on the line and makes the infuriating observation: “Well, if they were shrewd, they’d keep the door closed. Would they not maintain a sterile cockpit?”

To which Ong replied: “I think the guys are up there.”

Ms. Sweeney told her ground contact that the plane had radically changed direction; it was flying erratically and was in rapid descent. Mr. Woodward asked her to look out the window-what did she see?

“I see water. I see buildings. We’re flying low, we’re flying way too low,” Sweeney replied, according to the notes taken by Mr. Woodward. Sweeney then took a deep breath and gasped, “Oh, my God.”

At 8:46 a.m., Mr. Woodward lost contact with Amy Sweeney-the moment of metamorphosis, when her plane became a missile guided into the tower holding thousands of unsuspecting civilians. “So sometime between 8:30 and 8:46, American must have known that the hijacking was connected to Al Qaeda,” said Mike Sweeney. That would be 16 to 32 minutes before the second plane perforated the south tower.

Would American Airlines officials monitoring the Sweeney and Woodward dialogue have known right away that Mohamed Atta was connected to Al Qaeda?

“The answer is probably yes,” said 9/11 commission member Bob Kerrey, “but it seems to me that the weakness here, in running up to pre-9/11, is an unwillingness to believe that the United States of America could be attacked. Then you’re not putting defensive mechanisms in place. You’re not trying to screen out people with connections to Islamic extremist groups.”

Peg Ogonowski, the widow of Flight 11’s captain, John Ogonowski, knew both Betty and Amy very well. “They had to know they were dealing with zealots,” she said. “The words ‘Middle Eastern hijackers’ would put a chill in any flight-crew member’s heart. They were unpredictable; you couldn’t reason with them.”

Ms. Ogonowski knew this from her nearly three decades of experience as a flight attendant for American. She and her husband had dreamt of the time in the not-so-distant future when their teenage children would be old enough that the couple could work the same flight to Europe and enjoy layovers in London and Paris together. She had been scheduled to fly Flight 11 on Sept. 13. After Sept. 11, she imagined herself in Sweeney’s shoes: “When Amy picked up the phone-she was mother of two very young children-she had to know that, at that point, she might be being observed by another hijacker sitting in a passenger seat who would put a bullet through her head. What she did was incredibly brave.”

How, then, could the commission have missed-or ignored-crucial facts that this very first of the first responders communicated to officials on that fateful day?

“It seems amazing to me that they didn’t know,” said Mrs. Ogonowski. “The state of Massachusetts has an award in Amy Sweeney’s name for civilian bravery.” The first recipients were John Ogonowski and Betty Ong. A full-court ceremony was held on Sept. 11, 2002, in Faneuil Hall in Boston, with Senators Kennedy and Kerrey and the state’s whole political establishment in attendance.

Even the F.B.I. has recognized Amy Sweeney by bestowing on her its highest civilian honor, the Director’s Award for Exceptional Public Service. “Mrs. Sweeney is immeasurably deserving of recognition for her heroic, unselfish and professional manner in which she lived the last moments of her life,” according to the F.B.I.

What her husband wants to know is this: “When and how was this information about the hijackers used? Were Amy’s last moments put to the best use to protect and save others?”

“We know what she said from notes, and the government has them,” said Mary Schiavo, the formidable former Inspector General of the Department of Transportation, whose nickname among aviation officials was “Scary Mary.” Ms. Schiavo sat in on the commission’s hearing on aviation security on 9/11 and was disgusted by what it left out. “In any other situation, it would be unthinkable to withhold investigative material from an independent commission,” she told this writer. “There are usually grave consequences. But the commission is clearly not talking to everybody or not telling us everything.”

This is hardly the only evidence hiding in plain sight.

The captain of American’s Flight 11 stayed at the controls much of the diverted way from Boston to New York, sending surreptitious radio transmissions to authorities on the ground. Captain John Ogonowski was a strong and burly man with the instincts of a fighter pilot who had survived Vietnam. He gave extraordinary access to the drama inside his cockpit by triggering a “push-to-talk button” on the aircraft’s yoke (or wheel). “The button was being pushed intermittently most of the way to New York,” an F.A.A. air-traffic controller told The Christian Science Monitor the day after the catastrophe. “He wanted us to know something was wrong. When he pushed the button and the terrorist spoke, we knew there was this voice that was threatening the pilot, and it was clearly threatening.”

According to a timeline later adjusted by the F.A.A., Flight 11’s transponder was turned off at 8:20 a.m., only 21 minutes after takeoff. (Even before that, by probably a minute or so, Amy Sweeney began her report to American’s operations center at Logan.) The plane turned south toward New York, and more than one F.A.A. controller heard a transmission with an ominous statement by a terrorist in the background, saying, “We have more planes. We have other planes.” During these transmissions, the pilot’s voice and the heavily accented voice of a hijacker were clearly audible, according to two controllers. All of it was recorded by a F.A.A. traffic-control center in Nashua, N.H. According to the reporter, Mark Clayton, the federal law-enforcement officers arrived at the F.A.A. facility shortly after the World Trade Center attack and took the tape.

To this writer’s knowledge, there has been no public mention of the pilot’s narrative since the news report on Sept. 12, 2001. Families of the flight crew have only heard about it, but when Peg Ogonowski asked American Airlines to let her hear it, she never heard back. Their F.A.A. superiors forbade the controllers to talk to anyone else.

Has the F.B.I. turned this critical tape over to the commission?

At the commission’s January panel on aviation security, two rows of gray suits filled the back of the hearing room. They were not inspectors general of any of the government agencies called to testify. In fact, said Mary Schiavo, there is no entity within the administration pushing any consequences. The gray suits were all attorneys for the airlines, hovering around while the big bosses from American and United gave their utterly unrevealing testimonies.

Robert Bonner, the head of Customs and Border Protection, finally shot back at the panel with a startling boast.

“We ran passenger manifests through the system used by Customs-two were hits on our watch list of August 2001,” Mr. Bonner testified. “And by looking at the Arab names and their seat locations, ticket purchases and other passenger information, it didn’t take a lot to do a rudimentary link analysis. Customs officers were able to ID 19 probable hijackers within 45 minutes.”

He meant 45 minutes after four planes had been hijacked and turned into missiles. “I saw the sheet by 11 a.m.,” he said, adding proudly, “And that analysis did indeed correctly identify the terrorists.”

How has American Airlines responded? According to the widower Mike Sweeney, “Ever since Sept. 11, AMR [the parent company of American Airlines] just wants to forget this whole thing happened. They wouldn’t allow me to talk to Michael Woodward, and five months or so: they let him go.” The Families Steering Committee urged the commission to interview Michael Woodward about the Sweeney information, as did Ms. Ong’s brother, Harry Ong. A couple of days before the hearing on aviation security, a staffer did call Mr. Woodward and ask a few questions. But the explosive narrative offered by Amy Sweeney in her last 23 minutes of life was not included in the 9/11 commission’s hearing on aviation security.

The timeline that is most disturbing belongs to the last of the four suicide missions-United Airlines Flight 93, later presumed destined for the U.S. Capitol, if not the White House. Huge discrepancies persist in basic facts, such as when it crashed into the Pennsylvania countryside near Shanksville. The official impact time according to NORAD, the North American Air Defense Command, is 10:03 a.m. Later, U.S. Army seismograph data gave the impact time as 10:06:05. The F.A.A. gives a crash time of 10:07 a.m. And The New York Times , drawing on flight controllers in more than one F.A.A. facility, put the time at 10:10 a.m.

Up to a seven-minute discrepancy? In terms of an air disaster, seven minutes is close to an eternity. The way our nation has historically treated any airline tragedy is to pair up recordings from the cockpit and air-traffic control and parse the timeline down to the hundredths of a second. But as Mary Schiavo points out, “We don’t have an NTSB (National Transportation Safety Board) investigation here, and they ordinarily dissect the timeline to the thousandth of a second.”

Even more curious: The F.A.A. states that it established an open phone line with NORAD to discuss both American Airlines Flight 77 (headed for the Pentagon) and United’s Flight 93. If true, NORAD had as many as 50 minutes to order fighter jets to intercept Flight 93 in its path toward Washington, D.C. But NORAD’s official timeline claims that F.A.A. notification to NORAD on United Airlines Flight 93 is “not available.” Why isn’t it available?

Asked when NORAD gave an order for fighter planes to scramble in response to United’s Flight 93, the air-defense agency notes only that F-16’s were already airborne from Langley Air Force Base in Virginia to intercept American’s Flight 77. The latter jet heaved into the Pentagon at either 9:40 a.m. (according to the F.A.A.) or at 9:38 a.m. (according to NORAD). Although the F-16’s weren’t in the skies over Washington until 9:49, the question is: Did they continue flying north in an attempt to deter the last of the four hijacked jets? The distance was only 129 miles.

The independent commission is in a position to demand such answers, and many more. Have any weapons been recovered from any of the four downed planes? If not, why should the panel assume they were “less-than-four-inch knives,” the description repeatedly used in the commission’s hearing on aviation security? Remember the airlines’ first reports, that the whole job was pulled off with box cutters? In fact, investigators for the commission found that box cutters were reported on only one plane. In any case, box cutters were considered straight razors and were always illegal. Thus the airlines switched their story and produced a snap-open knife of less than four inches at the hearing. This weapon falls conveniently within the aviation-security guidelines pre-9/11.

But bombs? Mace or pepper spray? Gas masks? The F.B.I. dropped the clue that the hijackers had “masks” in a meeting with the Four Moms from New Jersey, the 9/11 widows who rallied for this independent commission.

The Moms want to know if investigators have looked into how the pilots were actually disabled. To think that eight pilots-four of whom were formerly in the military, some with combat experience in Vietnam, and all of whom were in superb physical shape-could have been subdued without a fight or so much as a sound stretches the imagination. Even giving the terrorists credit for a militarily disciplined act of war, it is rare for everything to go right in four separate battles.

Shouldn’t the families and the American people know whether or not our government took action to prevent the second attack planned for the command-and-control center in Washington?

Melody Homer is another young widow of a 9/11 pilot. Her husband, LeRoy Homer, a muscular former Air Force pilot, was the first officer of United’s Flight 93. The story put out by United-of heroic passengers invading the cockpit and struggling with the terrorists-is not believable to Melody Homer or to Sandy Dahl, widow of the plane’s captain, Jason Dahl. Mrs. Dahl was a working flight attendant with United and knew the configuration of that 757 like the back of her hand.

“We can’t imagine that passengers were able to get a cart out of its locked berth and push it down the single aisle and jam it into the cockpit with four strong, violent men behind the door,” said Ms. Homer. She believes that the victims’ family members who broke a confidentiality agreement and gave their interpretation of sounds they’d heard on the cockpit tape misinterpreted the shattering of china. “When a plane goes erratic, china falls.”

Now, the most disturbing disconnect of all: The F.A.A. and NORAD had at least 42 minutes to decide what to do about Flight 93. What really happened?

At 9:30 a.m., six minutes after receiving orders from NORAD, three F-16’s were airborne, according to NORAD’s timeline. At first, the planes were directed toward New York and probably reached 600 miles per hour within two minutes, said Maj. Gen. Mike J. Haugen, adjutant general of the North Dakota National Guard. Once it was apparent that the New York suicide missions were accomplished, the Virginia-based fighters were given a new flight target: Ronald Reagan Washington National Airport. The pilots heard an ominous squawk over the plane’s transponder, a code that indicates almost an emergency wartime footing. General Haugen says the F-16’s were asked to confirm that the Pentagon was on fire. The lead flier looked down and verified the worst.

Then the pilots received the most surreal order of the morning, from a voice identifying itself as a representative of the Secret Service. According to General Haugen, the voice said: “I want you to protect the White House at all costs.”

During that time, Vice President Richard Cheney called President George W. Bush to urge him to give the order that any other commercial airliners controlled by hijackers be shot down. In Bob Woodward’s book, Bush at War , the time of Mr. Cheney’s call was placed before 10 a.m. The Vice President explained to the President that a hijacked airliner was a weapon; even if the airliner was full of civilians, Mr. Cheney insisted, giving American fighter pilots the authority to fire on it was “the only practical answer.”

The President responded, according to Mr. Woodward, “You bet.”

Defense officials told CNN on Sept. 16, 2001, that Mr. Bush had not given authorization to the Defense Department to shoot down a passenger airliner “until after the Pentagon had been struck.”

So what happened in the period between just before 10:00 a.m. and 10:03 (or 10:06, or 10:07)-when, at some point, the United jet crashed in a field in Pennsylvania? Did the President act on Mr. Cheney’s advice and order the last and potentially most devastating of airborne missiles brought down before it reached the Capitol? Did Mr. Cheney act on the President’s O.K.? Did a U.S. fighter shoot down Flight 93? And why all the secrecy surrounding that last flight?

Melody Homer, the wife of Flight 93’s first officer, was at home in Marlton, N.J., the morning of Sept. 11 with their 10-month-old child. Within minutes of seeing the second plane turn into a fireball, Ms. Homer called the Flight Operations Center at John F. Kennedy International Airport, which keeps track of all New York–based pilots. She was told that her husband’s flight was fine.

“Whether or not my husband’s plane was shot down,” the widowed Mrs. Homer said, “the most angering part is reading about how the President handled this.”

Mr. Bush was notified 14 minutes after the first attack, at 9 a.m., when he arrived at an elementary school in Sarasota, Fla. He went into a private room and spoke by phone with his national security advisor, Condoleezza Rice, and glanced at a TV in the room. Mrs. Homer’s soft voice curdles when she describes his reaction: “I can’t get over what Bush said when he was called about the first plane hitting the tower: ‘That’s some bad pilot.’ Why did people on the street assume right away it was a terrorist hijacking, but our President didn’t know? Why did it take so long to ground all civilian aircraft? In the time between when my husband’s plane took off [at 8:41 a.m.] and when the second plane hit in New York [9:02 a.m.], they could have turned back to airfield.”

In fact, the pilots of Flight 93 are seldom mentioned in news reports-only the 40 passengers. And Mrs. Homer says that hurts. “My husband fought for his country in the Persian Gulf War, and he would have seen his role that day as the same thing-fighting for his country. It’s my belief, based on what I’ve been told by people affiliated with the Air Force, that at least one of the pilots was very instrumental in the outcome of that flight. I do believe the hijackers may have taken it down. But stalling the impetus of the plane so it didn’t make it to the Capitol or the White House-that was one of the pilots.”

Melody LeRoy later learned from a member of the Air Force who worked with her husband that “a couple of weeks before the incident, they were all sitting around and talking about the intelligence that was filtering through the military that something big was going to happen. For all of this to get ignored,” she said as she swallowed a sob, “it’s difficult to excuse that.”

John Lehman, former Secretary of the Navy and one of the most active interrogators among the commissioners, was told of some of the issues raised in this article. “These are exactly the right questions,” he said. “We have to put all these details together and then figure out what went wrong. Who didn’t do their job? Not just what was wrong with the existing system, but human beings.”

After 14 months of watching while commissioners politely negotiated with a White House that has used every known ruse and invented some new ones to evade, withhold and play peekaboo with the commissioners, the Four Moms and their Families Steering Committee feel frustrated almost to the boiling point.

Who is going to take a long, hard look at the policy failures and the failures of leadership? This seems to be where some members of the 9/11 commission are heading. Commission member Jamie Gorelick, winding up after the two-day hearings in January, said she was “amazed and shocked at how every agency defines its responsibility by leaving out the hard part.” She blasted the F.A.A. for ducking any responsibility for the prevention of terrorism. “We saw the same attitude in the F.B.I. and C.I.A.-not to use common sense to evaluate a mission and say what works and what doesn’t.”

Finally, Ms. Gorelick addressed a pointed question to James Loy, the deputy secretary of the Department of Homeland Security, the vast, Brobdingnagian bureaucracy which now lashes together 22 federal agencies that didn’t talk to one another before the terrorist attacks.

“Who is responsible for driving the strategy to defeat Al Qaeda and holding people accountable for carrying it out?” Ms. Gorelick demanded.

“The President is the guy,” said Mr. Loy. “And the person next to the President, who is the national security advisor.”

The widows are furious that Dr. Rice was allowed to be interviewed in private and has not agreed-nor been subpoenaed-to give her testimony, under oath, before the American people.

When 9/11 commission chairman Tom Kean gave his sobering assessment last December that the 9/11 attacks could have been prevented, the Bush White House saw the bipartisan panel spinning out of its control. In the President’s damage-control interview with NBC’s Tim Russert last weekend, Mr. Bush was clearly still unwilling to submit to questioning by the 9/11 commission. “Perhaps, perhaps,” was his negotiating stance.

Asked why he was appointing yet another commission-this one to quell the uproar over why we attacked Iraq to save ourselves from Saddam’s mythical W.M.D.-the President said, “This is a strategic look, kind of a big-picture look about the intelligence-gathering capacities of the United States of America …. Congress has got the capacity to look at the intelligence-gathering without giving away state secrets, and I look forward to all the investigations and looks.”

Congress has already given him a big-picture look-in a scathing 900-page report by the joint House and Senate inquiry into the intelligence failures pre-9/11. But the Bush administration doesn’t look at what it doesn’t want to see.

“It is incomprehensible why this administration has refused to aggressively pursue the leads that our inquiry developed,” fumes Senator Bob Graham, the former co-chairman of the inquiry, which ended in 2003. The Bush White House has ignored all but one or two of the joint inquiry’s 19 urgent recommendations to make the nation safer against the next attempted terrorist attack. The White House also allowed large portions of the inquiry’s final report to be censored (redacted), claiming national security, so that even some members of the current 9/11 commission-whose mandate was to build on the work of the congressional panel-cannot read the evidence.

Senator Graham snorted, “It’s absurd.”