NEW YORK — Two hijacked U.S. commercial planes slammed into the twin towers of the World Trade Center Tuesday, causing both 110-story landmarks to collapse in thunderous clouds of fire and smoke and killing possibly thousands of people starting their workday inside.
More than 40,000 people worked in the towers that were destroyed by the attacks, believed to be coordinated terrorist acts aimed at the heart of the nation's financial district.
Business was paralyzed, and markets were to be closed at least through Wednesday, one measure of the attack's impact.
The nightmarish onslaught began when the north tower was hit by a plane at about 8:45 a.m. EDT . A second plane hit the southern tower about 15 minutes later, triggering a fireball in the side of the building.
The planes blew gaping holes in the sides of each tower, and the upper floors of both towers exploded into flames.
The south tower imploded in a sickening burst of smoke, glass and metal about an hour later, and the north tower collapsed with a roar a few minutes after that.
Late Tuesday afternoon, a third Trade Center office building, a 47-story structure that had been evacuated, also collapsed.
Where the towers once stood at the southern tip of Manhattan, there was nothing but twisted steel, rubble, flames, smoke and a gaping hole in the skyline.
BUSH SAYS THOUSANDS DEAD
President Bush late Tuesday gave the first official estimate of the death toll.
"Thousands of lives were suddenly ended by evil, despicable acts of terror," Bush said in a five-minute televised address to the nation.
"When we get the final number, it will be more than we can bear," said New York City Mayor Rudolph Giuliani, adding that a "tremendous number of lives" were lost.
"The numbers will be very, very high," he said.
During the nearly two-hour period after the planes hit and before the two burning towers fell, people could be seen jumping from the highest floors.
"Bodies were just dropping, jumping. They were jumping like, first it was two. And, then, another one, and another one. I couldn't look," said one witness.
"I don't know if they were already dead or just going to die," added Ellen Leon, who watched from her nearby office.
Before the buildings collapsed, a person who answered the phone on the trading floor at dealer-broker Cantor Fitzgerald, near the top of the World Trade Center, said, "We're ... dying" and hung up. There was screaming and yelling in the background. A follow-up call was not answered.
Fleeing victims and onlookers who stopped to watch the first fires gasped and wailed when the towers unexpectedly fell.
"We were talking about how amazing the architecture was that it was still standing with that huge gaping hole in it, and then it just crumbled," said one onlooker.
The planes appeared to be part of a coordinated attack on U.S. centers of power, as another plane crashed at the Pentagon and one other airliner crashed in Pennsylvania.
Bush said Tuesday he would "make no distinction" between those who plotted the attacks and their hosts.
"These acts of mass murder were intended to frighten our nation into chaos and retreat, but they have failed. Our country is strong. Terrorist acts can shake the foundation of our biggest buildings, but they cannot touch the foundation of America," he said.
American Airlines said two of its planes crashed with 156 people aboard, and United Airlines said two flights with 110 people crashed.
Witness Rob Nelson said he clearly saw the red and blue AA logo of American Airlines on the first plane. "The plane looked strange. It was flying very low, heading south, and it hit the north side of the building," he said.
More than 300 firefighters who rushed to the scene after the planes first struck were missing and feared dead after the towers fell, authorities said in a late-night briefing.
MISSING WORKERS
At insurance brokerage firm Marsh & McLennan, only 500 of its 1,700 workers in the World Trade Center were accounted for, a spokeswoman said. The Trade Center's largest tenant, Morgan Stanley, had 3,500 employees on 25 floors.
The 28-year-old towers—part of the largest commercial complex in the world that housed financial and government offices as well as an extensive subway and commuter train station underneath—were the scene of a 1993 car bomb attack that killed six people and injured more than 1,000 people.
As darkness fell, the eerie scene was lit by huge banks of bright industrial klieg lights to help rescuers. Some used bulldozers and heavy equipment to clear mud and debris.
Late evening, two police officers were pulled alive from the rubble, the mayor said in a late night briefing.
Two other victims trapped inside had called for help on cell phones and said there were others alive with them, he said.
"We have not given up hope we will find people alive," the mayor said.
An out-of-work construction worker who helped search for victims said the chances of surviving were remote.
"Inside, forget about it. There's nobody to be found down there. Not in the tower I was in," said Gary Louisa after he was taken to a hospital for dehydration and smoke inhalation.
Temporary morgues were set up at hospitals and on piers along the Hudson River. Six people were confirmed dead at two hospitals.
More than 600 people were treated at hospitals, including 200 critically injured, and 2,000 "walking wounded" were taken by ferry across the Hudson River to New Jersey for treatment, the mayor said.
One doctor reported treating a World Trade Center maintenance worker who suffered such bad memory loss that he had no idea the buildings had collapsed.
Hospitals awaited for waves of more patients but, in an ominous sign, few came.
"I think so many people are dead. It's a bad sign that there are no mass casualties," said Dr. James Dillard at St. Vincents Hospital.
As the towers fell, streets and nearby buildings in the dense neighborhood were bombarded with concrete and twisted metal. Blinding dust filled the narrow streets three stories high, covering and choking fleeing victims.
Mike Wilson, who worked on the 51st floor of one tower, said after the first plane hit, some of his co-workers opted to wait in their offices because the stairwells were so crowded.
"People figured that once the plane hit, that was it. People didn't think that the buildings were going to fall down," he said. "Those people and all the firemen going up, well, they are all dead."
Survivor George Oakley said: "When I got outside, there was literally a snowstorm of paper, clothing, ladies shoes, and I even saw a brown burning jacket falling to the ground."
All over the city, people gathered in crowds to gape at the billowing smoke where the twin towers once stood. Strangers stood together, shocked and in tears, listening to radio reports played from cars parked on the streets.
Onlookers reported seeing body parts and decapitated bodies amid the debris. A nearby Marriott hotel was engulfed in flames.
Authorities practically sealed off New York, closing and evacuating the three major airports and setting up roadblocks to stop all inbound traffic on tunnels and bridges.
The city emptied as businesses closed and streams of frightened people made their way home by walking across bridges to Brooklyn and Queens.
The mayor ordered downtown Manhattan off-limits to civilians and instructed people to stay home Wednesday, and police blocked all traffic below 14th Street.
Churches held services to pray for the missing.
"We are all undergoing right now something that we have had nightmares about, but probably thought would not happen," the mayor said.
Gov. George Pataki declared a state of disaster emergency and called in the state National Guard.
Amid the tragedy were any number of heroes.
"I started going down the steps," said one survivor. "There was a woman in a wheelchair. I got her into a strap of the wheelchair and just carried her down the steps, down 68 floors, man. We got lost on the fifth floor. It was chaos."
The twin towers were a popular tourist destination, but neither the observations decks nor the well-known "Windows on the World" restaurant were open at the time of the impact.