The Big Moment: Probably some idiot amateur pilot, I thought. Then a second plane took aim

US terror attacks, 11 September 2001

(AP)

11 September 2001 was a bright autumn morning on America's east coast. At 8.48am, however, the world changed. Two planes, piloted by terrorists, flew into the twin towers of the World Trade Centre in New York; a third plane crashed into the Pentagon in Virginia. War had come to America. The initial shock soon gave way to fear of further attacks, as an unprecedented emergency operation got underway.

My wife called and told me to turn on CNN. For a moment, normality refused to let go; probably some idiot amateur pilot, I thought; then another plane took aim and flew like a missile into the South tower, and you knew this was an event unlike anything before. The third plane was flying too fast and too low, then disappeared below the fold of the hill. Then there was an enormous explosion as the plane hit the Pentagon.

It was the day America's luck ran out. The day you suspected might one day come, but could not comprehend when it did – neither the dimension of the tragedy nor the motives of those who did it. And above all, perhaps, how they did it.

Amid the numbed bewilderment and horror that united America yesterday, you could grasp one thing alone with certainty. This was the biggest, most murderous and most spectacular terrorist onslaught in history, unleashed against the United States – a sequence of co-ordinated attacks against targets in New York and Washington which destroyed the World Trade Centre in New York, blew up a part of the Pentagon, the symbol of US military might, and left untold hundreds, more probably thousands, dead and injured.

Along the east coast it was the most beautiful early autumn day. Summer's humidity was just a memory, just a gentle breeze and the skies a limpid blue. But at precisely 8.48am it became the day when America's luck ran out – a ghastly day when war came to the continental superpower separated by great oceans from a less fortunate world.

It is not the first war, for America has experienced an Independence War and a Mexican war, as well as a terrible civil war which took 600,000 lives. But if early indications are borne out, this will be America's first taste of war brought to it from across the seas, an act of terrorist vengeance all the more frightening because the enemy is invisible and unknown. Events previously confined to Tom Clancy novels and Hollywood summer scare movies became the shattering, bewildering reality of an ordinary autumn morning.

Recount it in cold print, and you are unable to believe it. In numbing, bewildering sequence, two hijacked aircraft – one an American Airlines 767 – crashed into each of the two World Trade Centre towers in New York; then another commercial plane smashed into the Pentagon in Washington and a fire erupted on the Mall, then word of a fourth crash in Pennsylvania. Within two hours both towers, emblems of American wealth and influence, were no more.

No one, not the man on the street, not the smart gentlemen at the country's myriad intelligence agencies, nor the man in the White House had the faintest notion of what was happening. Washington, capital of the world's overwhelming superpower, was utterly paralysed. The White House, the State Department, the Capitol, the CIA's headquarters in Virginia, every other federal building – all were evacuated. Traffic around the centre was gridlocked as people fled their offices and tried to drive home. Cellphone circuits collapsed.

Every main airport across the US was shut, all international flights were diverted to Canada. Chaos reigned everywhere, as the devastating chain of events – unfolding in the space of less than an hour – swamped the country's ability to cope. In New York, where the human toll was highest, the city was brought to a dreadful standstill, as mighty clouds of smoke swirled around the smouldering ruins. Hospitals were overwhelmed, bloodbanks drained; at this most basic level, the scale of what had just happened defied understanding.

The day dwarfed anything in recent American history. In its time, the 1993 terrorist attack that killed six people at the World Trade Centre sent shivers through the country as a portent of what might come. What did come was the 1995 Oklahoma City bombing, not the work of a foreign terrorist, but a homemade atrocity carried out by the icily calculating Timothy McVeigh, in which more than 160 people died.

However, the blown-out facade of Oklahoma's Alfred P Murrah building, in retrospect, was a child's macabre amusement. Yesterday, the normal yardstick of tragedy, the number of people killed, meant nothing. This time the calculation was a ghoulish arithmetic with too many variables. Four, maybe five commercial jets, each perhaps full of people who boarded them a few minutes, an hour at the most, beforehand, unsuspecting of the terror and death that awaited them. How many were aboard?

Hundreds, thousands, no one knew. Normally in the US one big airline crash occurs a year; in a good year there are none. This time there were four (at least) within the space of an hour – three at the highest profile targets imaginable, the fourth, a United 757 from Newark, New Jersey, bound for San Francisco, coming to grief in the heart of American rural normality, at Shanksville in the rolling hills of western Pennsylvania. What target was it aiming at: Chicago or some other symbol of US power and ebullience?

And then the mayhem at the Pentagon, and the building's army planning wing that took the direct hit from what now appears to be a Boeing 767 ploughing into it. In the uncannily calm words of a witness who watched the unbelievable as she was driving on Interstate 395 on her regular commute into downtown Washington around 9am on a pristine morning: "It was a commercial plane. It was flying too fast and too low. Then it just disappeared below the fold of the hill. The next thing, there was an enormous explosion." Such was one air-traffic movement on the morning of 11 September 2001 in the brilliant sunny skies of Washington in autumn.

And then New York, where it all started. "Turn on CNN!" my wife called just before 9am: "A plane's hit the World Trade Centre." I did – but for a moment, despite the smoke billowing from the side of the building, normality still refused to let go. Probably some idiot amateur pilot, I thought: didn't a plane hit the Empire State Building back in the Thirties, and only the other day didn't some hang-glider get tangled up on the crown of the Statue of Liberty?

But then another plane took aim and flew like a missile into the other, South tower of the Trade Centre. You knew this was something different; an event unlike anything before, no act of God or human error, but an utterly deliberate aerial version of a double-suicide bombing, directed at the best-known symbol of American commercial might.

Even the TV anchors could not believe what they were witnessing. It was Hollywood for real, in which the fire burnt as bright yellow and the smoke as acridly black as in the movies – except this was real life. Every day, 20,000 people work in the Trade Centre: how many were trapped when the terrorists struck?