The Flight 93 passengers had walked down the concourse of Terminal A, where they breezed past the security gate, then walked the 100 yards to a long circular hallway from which the boarding ramps jutted out like spokes.

At Gate 17, they strode another 70 feet down the jetway, made a left turn, and were inside the Boeing 757. The plane pulled away from the gate on time. Then it sat. It was a 110-foot-long space that different people from different worlds were meant to share for the six-hour flight across a continent filled with immigrants and their descendants. Hilda Marcin, 79, took an aisle seat in row 17. A retired special education teacher's aide, Marcin was moving to Danville, Calif., to live with her daughter's family. Her older daughter, Elizabeth Kemmerer, had driven her to the airport, waited with her until 7:30, then seen her mother off to a new life. Thomas Burnett Jr., 38, had been living in planes for the preceding six days. A senior vice president and chief operating officer for a medical research company in San Ramon, Calif., he had made it home at 4 p.m. Sept. 5 for dinner, left at 11 p.m. that night, stopped in Minnesota, then spent the weekend moving deer stands around on land he owned in Wisconsin. He planned to go back in November to hunt deer. He installed himself in seat 4C, first class.

Christine Snyder's husband of two months was waiting for her back in Kailua, Hawaii, where she worked as an arborist, planting trees and landscaping public places, bringing human order to a natural paradise. On the drive to the airport she marveled at the billboards, wires, transmission lines, industrial plants -- things she didn't see back home.

Also on board were four men from an entirely different world. Ziad Jarrah, their leader, had been born in the Bekaa Valley of Lebanon in 1975. Outwardly, it would have been hard to know the turmoil that boiled inside him. Born into an apolitical and secular family of Sunni Muslims, Jarrah attended Christian schools as a youth, studied aviation in Europe and told the man in Florida who had taught him close-quarters hand-fighting that he loved living in America. "Find ways to blend in with your opponent and control him," the instructor, Bert Rodriguez, had told Jarrah back in May, when he walked into US-1 Fitness, a gymnasium in Dania Beach, Fla., and paid $500 cash for the course. Now, settling into a seat in first class, Jarrah had blended in. No one on board would have guessed that back in the Florida apartment he'd left four days earlier, Jarrah had set up a full-size, cardboard replica -- three panels in all -- of the cockpit of the airplane they had just boarded. Nobody could have known he was carrying a global positioning satellite receiver to help him track the plane's course. No one could have known that he and his three companions, seated throughout the plane, had stayed in the same hotel as some of the passengers the night before, eating at the best of its three restaurants, paying cash for seven rooms, meeting with other men who would depart on missions investigators are still trying to figure out.

United Flight 93 groaned down Runway 4-Left, pulled up and banked to the west. From the right side of the plane, passengers would have seen lower Manhattan where, on overcast days, the only thing poking above the clouds were the twin pillars of the World Trade Center. On this day, everything was clear.

No one could have known that, in the skies over Pennsylvania, the worlds of Hilda Marcin, of Thomas Burnett, of Christine Snyder, of Ziad Jarrah, would meet in a cataclysm of cool rage and desperate courage, as passengers tried to take back their airplane, all the time unaware that an Air Force jet, scrambled from a base in Virginia, was closing in with orders to shoot the plane down before it got to Washington, D.C.

By the time United Flight 93 was in smoldering pieces in a field outside the Somerset County village of Shanksville, the F-16 was 14 minutes from the range at which it could have brought down the 757 with heat-seeking missiles. Flight 93 became an asterisk to a day of horror that claimed almost 5,000 lives, toppled buildings that stood like a twin Colossus on the New York shore, took down one side of the Pentagon, and ushered in a war without rules against an enemy without a state.

What made Flight 93 different was a decision reached somewhere over the skies of Western Pennsylvania, after passengers learned on cell phones that they were likely to be flown into a building as the fourth in a quartet of suicide attacks.

They decided to fight.

They became the first casualties in a strange new combat against an enemy as old as hatred and as unclear as the muffled shouts and groans investigators would later hear on the cockpit voice recorder dug out of a reclaimed strip mine on a Pennsylvania hillside.

This is their story.

In December 1999, 40 people were living lives as ordinary and remarkable as those doled out to anyone by fortune's hand. John Talignani was retired after 20 years of serving drinks at a Manhattan steakhouse. He would sit in front of his 55-inch television in his Staten Island home and order things on QVC. He couldn't resist. He had two bread makers. Toasters. A pasta maker. Baseball memorabilia.

Sandra Waugh Bradshaw was juggling dual careers -- flight attendant and mother. She was home in Greensboro, N.C. with her year-old daughter, Alexandria. In the coming year, her son Nathan would arrive.

Alan Beaven was practicing law in San Francisco.

Kristin Gould White was researching medical history at Ivy League schools.

Richard Guadagno was photographing wildlife.

Pilot LeRoy Homer Jr. was living life as a newlywed.

In the town of Abha, Saudi Arabia, a skinny, 21-year-old student of Islamic law -- it is called Sharia -- was leaving on a religious trip. Under the rules of Islam, every man must, once in his life, travel to the city of Mecca. Then there were the other trips, the optional, minor pilgrimages known as "Umra." It was on Umra that Ahmed Al Nami left for Mecca. Before entering the city, Al Nami would stop, perform the rituals of purity, then enter, pray, and walk on holy ground. But he was supposed to come home. For almost two years his family would hear nothing from him. His religious journey was about to take him several stops beyond a holy city.

Melodie Homer doesn't know if her husband kissed her goodbye. She had spent most of Monday, Sept. 10, sick in bed. LeRoy Homer stayed up late watching television. By the time he got to bed, she was drifting off to sleep. The alarm sounded at 4:45 Tuesday morning. She could hear the shower running, the sounds of a man dressing quietly in the bathroom, trying not to awaken his wife, or their 11-month-old daughter, Laurel, who slept in another room. LeRoy Homer put on dark blue trousers, a white shirt, blue tie, and a United Airlines jacket with epaulets. He was now First Officer LeRoy Homer, who would sit in the righthand seat of the cockpit of a Boeing 757. He was starting the day in Marlton, N.J., and was to end his morning in San Francisco.

Homer got into his Toyota 4-Runner and began the 75-minute drive north to Newark International Airport.

Alan Beaven was up at 4. He had a rental car to drop off at the airport from the Catskills home he was sharing with his wife and 5-year-old daughter, Sonali. Beaven was born in New Zealand. He lived in England for a time and worked as a prosecutor for Scotland Yard. Now he was an environmental lawyer, with an office in San Francisco, and he had one last case to try before departing with his family to do volunteer work in India. His world view was summed up in a motto he'd taped to the wall of his New York office: "Fear -- who cares?" Before he left, Beaven woke his wife, Kimi, to say goodbye. "I'm going to win this case for you," he said. She pulled him toward her. "All I want from California is for you to come back safe and sound," she said. Beaven left with a suitcase and a bag of court papers, but no cell phone. He didn't carry one.

As LeRoy Homer was traveling north on the New Jersey Turnpike, Christine Snyder and Mary Steiner were in a limousine, going south, from a friend's apartment in Manhattan. The pair had slipped up to New York after attending the American Forestry Conference in Washington. The day before they left Manhattan, they took in a Broadway show, rode the Staten Island Ferry and drank Diet Cokes at the top of the tallest buildings on the East Coast. The view from the World Trade Center had been astonishing. When they reached the airport they split up.

Steiner was flying on Northwest. Snyder wanted to build up frequent flier miles on her United account. That morning, she called to check on her flight, Flight 91, due to leave after 9 a.m. She moved up to Flight 93 for an earlier start. "See you tomorrow," Steiner called out to her friend.

Colleen L. Fraser, 51, dressed for comfort that morning. At 4 1/2 feet tall, a survivor of childhood surgeries for an inherited bone condition, she walked with a cane, flew with trepidation and fought for the disabled with ferocity. She was vice chairwoman of the New Jersey Developmental Disabilities Council, a woman with a flame-red, spiked crewcut who kept a small copy of the Constitution that she would brandish when confronted with anything that struck her as unjust. Her sister Christine dropped her off shortly before 7 a.m. They marveled at the clear weather.

At the Airport Marriott Hotel, visible from Terminal A, Christian Adams had said good night on Monday to Carol Sullivan, director of the German Wine Information Bureau, and Sullivan's assistant, Caroline Von Bistram. The trio were to travel the next day to San Francisco for an annual wine-tasting. Adams was deputy director of the German Wine Institute, visiting on business from Biebelsheim in southern Germany. "My assistant and I had to leave the hotel by 6 a.m. to catch the hotel shuttle going over to the airport," Sullivan said. "He'd been joking with us the night before that, since his flight was 15 minutes later, he could sleep 15 minutes longer and probably wouldn't be seeing us in the lobby." Apparently, Adams did sleep a little longer. Sullivan and Von Bistram boarded the shuttle without seeing him. Somewhere upstairs at the Marriott, other passengers were gathered.

Ziad Jarrah had come to the hotel a day earlier and paid cash for seven rooms. He and his companions ate the night before at Priscilla's, the hotel's upscale restaurant, where prime steak sells for $34, baby New Zealand lamb goes for $30, and cream of watercress soup starts at $10. "They paid cash for everything," said one hotel waiter.

With Jarrah was his roommate from Florida, Ahmed Al Haznawi, a 20-year-old student from Baljurshi, Saudi Arabia, along with Al Nami, the man who disappeared on his visit to Mecca, and Saeed Al Ghamdi, a young man about whom almost nothing is known. Since arriving in the United States in late 1999, Jarrah had studied at two south Florida flight schools. His family in Lebanon told investigators they regularly sent him money -- sometimes as much as $2,000 a month. Before moving to the United States, Jarrah studied aeronautical engineering in Hamburg, Germany, where he became close to another Muslim student named Mohamed Atta, later identified as the man who flew American Airlines Flight 11 into the World Trade Center.

Atta was fiery, religious, almost fearfully disdainful of women. It changed Jarrah, who had received a largely non-religious upbringing. Jarrah's Turkish girlfriend, Aisle Senguen, told German investigators that Jarrah sometimes criticized her for becoming "too westernized," although he himself had attended Christian schools as a youngster, drank and fancied discotheques. After moving to Florida, Jarrah and his companions were regularly in touch with Atta, who dispensed thousands of dollars in living expenses through postal orders. Jarrah moved from apartment to apartment, rarely leaving a forwarding address.

On Sept. 5, Jarrah and Al Haznawi, the son of a Muslim prayer leader, visited Mile High Travel in Fort Lauderdale and booked two one-way tickets to Newark. Two days later, Al Ghamdi and Al Nami stopped at another Fort Lauderdale travel agency, Passage Tours, and paid $140 each for budget airline flights to Newark. The night before boarding Flight 93, in their hotel rooms, Jarrah would have opened a list of instructions, kept in a notebook that apparently was written by his old friend Atta. It instructed them to bathe, wear cologne, shave excess hair from their bodies and check the knives they carried. "You must make your knife sharp and you must not discomfort your animal during the slaughter," it read. "Completely forget something called 'this life.' The time for play is over and the serious time is upon us."

It instructed them to turn to two Suras -- chapters -- of the Koran, al Tawba and al Anfa, which translate to "Repentance" and "The Spoils of War." In Al-Anfa, the 32nd verse reads: Remember how they said:

"O Allah! If this is indeed

The Truth from Thee,

Rain down on us a shower

Of stones from the sky,

Or send us a grievous Penalty."

The crew of United Flight 93 gathered one hour before the scheduled take-off. Such meetings are routine. Pilot and first officer decide who will handle the takeoff and landing, who will work the radio and computers. Flight attendants go over the passenger manifest and decide who will work what sections of the cabin.

The pilot was Jason Dahl, 43, of Denver. Homer would fly alongside him as first officer. Dahl was planning to take his wife Sandy to London for their fifth wedding anniversary Sept. 14, and by moving up his flight schedule, they would have more time together overseas. Sandy, a United flight attendant, went onto United's computer system and shifted him to Flight 93. The night before he left Denver, Dahl took his wife downtown and told her to pick a car she liked. What he hadn't told her was, when he got back home on Friday, he also was having a baby grand piano delivered.

On Sept. 10, Dahl flew as a passenger in business class on his way to Newark. He sat next to Rob Quillen, a businessman from Lincoln, Neb., who knew he was next to someone important when an attendant brought Dahl a beer before anybody else on the plane had been served. The pair struck up a conversation about the safety of flying. Quillen said his biggest fear was engine failure. Dahl told him that had happened to him but that he'd made an emergency landing without trouble. Dahl's biggest worry, as Quillen remembered it, was landing in the rain. The massive wheels could hydroplane. The conversation moved on to stock car racing, and Quillen, who was scheduled to be a host at a NASCAR event in Kansas City a week later, got Dahl's cellphone number. He planned to send along tickets for Dahl and his 15-year-old son from a previous marriage. "I'll talk to you next week and get those tickets out to you," Quillen told him.

Deborah Welsh was the purser -- the key attendant who stands in front, makes announcements and oversees the others. Wanda Green wasn't originally supposed to be on Flight 93. The 49-year-old divorced mother of two grown children had been scheduled to fly Sept. 13, but Green, who also worked as a real estate agent, realized she had to handle the closing of a home sale Sept. 13. She'd phoned her best friend, fellow flight attendant Donita Judge, who opened United's computerized schedule and shifted Green to the Sept. 11 flight. It was what attendants call a "senior trip" -- with few passengers and a layover in San Francisco where Green could visit family. "I was feeling good about that," Judge said. Green drew Door 2, the first row of coach, from which she would work the first-class aisles with Lorraine Bay, a 37-year veteran with United. Sandy Bradshaw, 38, would work the back of the plane, in economy class. After the first of her two children was born two years ago -- she also had a 16-year-old stepdaughter -- Bradshaw cut back on her workload. Her husband, Phil, a US Airways pilot, urged her to quit. She was thinking about it. But after 11 years as an attendant, and a personnel file filled with complimentary letters from pleased passengers, she still loved to fly. She was in economy because she'd picked up Flight 93 late in the planning. Ordinarily, she liked working first class. It was a good fit with her gregarious ways. "She just liked the one-on-one that you have with people up there," Phil Bradshaw said. CeeCee Lyles, 33, of Fort Myers, Fla., had perhaps the most unusual resume among the flight crew. She'd been a police officer and detective for six years in Fort Pierce, Fla. In late 2000, she left that job to pursue her lifetime dream: to be a flight attendant.

The switch displeased some relatives. Air travel, they told CeeCee, seemed more dangerous than police work. Lyles laughed it off. She had married Lorne Lyles, a police officer in Fort Myers, and between them they were raising a blended brood of four boys: her sons Jerome Smith, 16, and Jevon Castrillo, 6, and Lorne's sons, Justin, 11, and Jordan, 9. When United posted her to Newark in February, CeeCee Lyles picked up an apartment with four other attendants, and commuted home to Florida when she was free. And in-between, there was the cell phone. "We talked about everything and nothing," Lorne Lyles said. "Stuff about the kids, the list of bills I had to pay and how much we missed each other."

The crew boarded its flight 35 minutes ahead of the scheduled departure. The attendants began preparing the in-flight breakfast. One passenger was late. Mark Bingham had overslept and his friend, Matthew Hall, drove madly from Manhattan to Newark. They screeched to a halt outside Terminal A at 7:40. Bingham leapt from the car, lugging the old, blue-and-gold canvas bag he'd used as a rugby player at the University of California at Berkeley a decade earlier.

United attendants reopened the door to the boarding ramp and let him on the plane. Bingham slipped into a seat in aisle 4-D, next to Thomas Burnett. Nine minutes after Hall dropped him off, Bingham picked up his cell phone. "Hey, it's me," he said. "Thanks for driving so crazy to get me here. I'm in first class, drinking a glass of orange juice."

Bert Rodriguez thinks it was the flier that drew in Ziad Jarrah. He turned up at US-1 Fitness in Dania Beach, just north of Miami, in May after Rodriguez put out a handbill saying, "Assert yourself." It explained that Rodriguez had trained police and federal agents in close-quarters hand-fighting. Most martial arts students don't train directly with Rodriguez, who has a staff of instructors. But Jarrah, Rodriguez said, "specifically came to train with me." He paid $500 cash for a series of 10 lessons. Then, when those were done, he returned and peeled off $500 in cash for another 10. At 5 feet, 11 inches and about 180 pounds, Jarrah surprised Rodriguez with his stamina. The training included flat-out fighting. At one point, the trainer went at the student with a baseball bat to teach him disarming techniques. The young man, who told Rodriguez he was training to become a pilot, could go 10, 15 or 20 minutes in unrelenting combat. The battle techniques Jarrah came to learn involved thinking -- figuring out ways to make an opponent's moves work against him; throwing attackers off-balance; keeping composure under stress. Jarrah, Rodriguez said, was very calm and a quick learner. "He was in very, very good shape. He was a great person to work with," Rodriguez said. "I told him, 'If you have someone to practice with, practice these techniques.' He told me, 'Oh, yeah, I have some roommates I can train with.' " Rodriguez told Jarrah to bring them in. He'd give a group discount. "He said no, they travel a lot." Between lessons, Jarrah, who carried a German passport and claimed to be Saudi, and Rodriguez, a 53-year-old Cuban-American, talked about the world. "We talked about business and leadership. We talked about employees," Rodriguez said. "He told me that he loved it here and that he had a girlfriend in Germany and he was planning to return there."

In August, Jarrah said he was planning some more travel. Rodriguez could not have known that the young man had written home to his family -- not in Saudi Arabia but in Beirut -- asking for $700. Investigators say the family told them it was "for fun." He planned to visit California.

Flight 93 was near cruising altitude when a system-wide message came over its monitor. United control warned pilots in the air of potential "cockpit intrusion" -- meaning some passenger might try to seize a plane. They acknowledged the message. A few minutes after 9 a.m., with the World Trade Center hundreds of miles behind it and now in flames, Flight 93 would have reached 31,000 feet and 515 mph.