For a weekday morning at Boston's Logan Airport, it was a relatively routine event: drivers in two cars got into a heated argument over a parking space.

The spat would have been forgotten with the thousands of similar altercations that happen every day, except that upon landing at his destination, one of the drivers looked at an airport television, saw that two of the planes hijacked had come from Boston, and remembered his parking space tiff had been with several men who appeared to be Arab.

A quick call to authorities gave police their first tip that would lead investigators from an airport parking lot to a pilot school in Florida to an apartment in Hamburg, Germany in a period of just over 24 hours - the start of the largest criminal inquiry in US history.

The white Mitsubishi from National Car Rental was important for what was found inside: a flight manual in Arabic that apparently led authorities to Huffman Aviation, a small pilot training school on a tiny airstrip in the west Florida beach town of Venice.

At 2:30 the next morning, FBI agents showed up at Huffman and walked out with records of two men, Mohammed Atta, 33, and Marwan al-Shehhi, 23, who had taken classes in small single-engine and twin-engine planes.

The same morning, agents showed up at the door of Drucilla Voss and her husband, Charles, a bookkeeper at Huffman. It appears the men had listed the Voss's home address as their own when renting the car. They had used a room in the house for a few days, but Drucilla found them rude. "They thought they could do anything they wanted," she said. But federal agents told the couple Mr Atta and Mr al-Shehhi were suspected of something far more vile than rudeness: they were on the passenger lists of the two planes which crashed into the World Trade Center and were suspected hijackers.

Huffman's owner, Rudy Dekkers, told investigators there was no way the men could fly Boeing jets after getting training at their small school, but he said the two had moved on to more sophisticated training elsewhere.

From there, federal officials fanned out across Florida, piecing together the hijackers' stay in the Sunshine State. That same night and early the next morning, several showed up in Hollywood, a resort town 20 miles north of Miami. At Shuckums Restaurant, bartenders and waitresses recognised the photos of the two men.

As a matter of fact, night manager Tony Amos recalled, the two men had been there a few days before. Both appeared drunk and got angry when they were asked to pay their bill by bartender Patricia Edrissi. Attempting to defuse things, Mr Amos approached the men and asked them if they were unable to pay the $48 liquor bill.

One of the men got angry, pulling a thick roll of cash from his pocket. "He said, 'I'm a pilot from American Airlines and I can afford to pay my bill'," recalled Ms Edrissi.

At the same time, elsewhere in Hollywood, agents Ronald Gaskins and Clinton Freely showed up at 1818 Jackson Street, where Mr Atta and Mr al-Shahhi had lived for a month early this summer. The two searched apartment 3A while two colleagues Tom Ryan and Randy Culp woke up Jean Luc Desjardins and Yolanda Lavoie, a couple who had owned the building. Between them, the agents managed to find the old rental application Mr Atta and Mr al-Shahhi had signed. Their previous address, listed on the paperwork: Hamburg, Germany.

Justice Department officials in Washington quickly informed their German counterparts. Within hours, German police had searched apartments where Mr Atta had lived and learned that both men had taken classes at Hamburg Technical University.

Reinhard Wagner, head of the Hamburg office of Germany's domestic intelligence service, said there was a broad network in the city of supporters of Saudi fugitive Osama bin Laden, the man US officials believe masterminded the entire plot: "They perform logistic functions for bin Laden, possibly by providing contacts or places to stay."

In all, an amazing feat of detective work: from an airport scuffle to the FBI's most wanted man in just over a day.

The stretch of road from Kabul to the eastern city of Jalalabad captures the history, culture, destruction and, above all, the militancy, that has rocked Afghanistan.

The 140km stretch can take up to four hours as drivers brave not only the potholes left behind from rocket attacks, but also portions of roads erased by the tanks and artillery vehicles that have ploughed it in more than two decades of war.

In the old days, successive Afghan kings used to travel up to Jalalabad, the winter capital, as snow covered the peaks surrounding Kabul. The life for the herdsmen dressed in traditional clothes, visible from afar with their characteristic Afghan turbans, ushering their sheep has remained almost unchanged for centuries.

The first hour after leaving Kabul in the morning can be a deceptive experience, driving on partly paved road with towering mountains on your right, a river deep down a ravine on your left, shouldered by another stretch of rugged mountains. There soon follows a longer stretch of road which must count among the world's most back-breaking journeys.

It is misleading for another reason. For not far from the mix of breathtaking beauty and serenity is the rugged terrain which could well become the site of America's next military engagement.

Hidden away in those mountains are some of the caves suspected by western intelligence officials of being the haven of the man many believe plotted and inspited the World Trade Center outrage.

It is here, many believe, that Osama bin Laden, runs his 'Al-Quaida organisation formed to conduct a tireless campaign against what it regards as the anti-Islamic American empire, patron of Israel.

While Mr bin Laden and his followers have long ago outgrown their reputation of a rag-tag army of angry young Islamic radicals from all over the Arab world, largely armed with AK-47 Kalashnikov assault rifles, the rugged terrain impresses few as a site for high-tech training, and definitely not the place to learn how to pilot a commercial aircraft. Regular daily supplies, such as food, are probably taken up only on the back of mules along the few winding paths vaguely visible from the road.

While the US has used its satellites for about three years searching for Mr bin Laden, his exact location has never been fully ascertained. He makes a habit of moving swiftly from camp to camp, despite a slight limp in his right leg from an injury, and an unconfirmed kidney condition which at least on one occasion triggered rumours that dialysis machines had to be brought in for treatment. There are also rumours that Mr bin Laden is surrounded by up to four look-alikes as a security precaution.

If America's quest for justice for those who died on September 11 takes its security and military forces into the inhospitable mountains of Afghanistan, it would not be the first time a powerful army has confronted an enemy there - often greatly to its regret.

To this day, children run up and down the corpses of Soviet tanks and other artillery vehicles left behind from Moscow's decade-long, disastrous attempt to subdue Afghanistan 20 years ago.

As on Friday Americans were mourning their loss and Congress was moving to authorise the use of military force, Pakistan was being asked to let warplanes fly over its territory.

And the Taliban, the fanatic movement that rules over most of Afghanistan, was threatening that war on them would bring revenge. As to the Arab militants, the companions of bin Laden, an Arab newspaper in London was reporting that they had already evacuated their mountain bases. The whereabouts of Osama bin Laden were a mystery.

Back in America, Captain Oganowski and scores of other airline crew and their passengers were remembered across America and the world on Friday. Elliott Nadel is at home in Bayside and Glenn Flood is working 12-hour days at the Pentagon.

At the same time more than the New York skyline will have changed for ever. Lawmakers discuss whether America's liberties are compatible with the fight against this mysterious enemy.

Americans have come to use aircraft as casually as buses, but that ease of movement may become a thing of the past as security measures make boarding a lengthy procedure.

As the horror of what some of their countrymen suffered burns into their memories, Americans may never look at a skyscraper in quite the same way again, either as places to work or to live.

Perhaps more fundamentally, they will look at their own safety differently. No more do the oceans that have kept America impregnable since the British attacked the White House in 1812 offer the security they once did. Like it or not, for good or for ill, all Americans now know they cannot shut themselves away from the rest of the world.

Written by:
Peter Thal Larsen
Richard Wolffe
Peter Spiegel
Victoria Griffith
Nancy Dunne
James Harding
Stephen Fidler
Farhan Bokhari
Gillian Tett
James Drummond
Mark Odell
Kevin Done
Abigail Rayner
Stephanie Kirchgaessner
Tally Goldstein

Part Two

Part One