CHICAGO -- Air traffic around the nation was halted Tuesday for the first time in history as stunned travelers watched televised pictures of the smoking wreckage of New York's World Trade Center and the Pentagon, both attacked by terrorists.

The Federal Aviation Administration ordered all outbound flights grounded following the fiery twin disaster at the World Trade Center around 9 a.m. The FAA said the ban would not be lifted until Wednesday at noon ET, at the earliest.

All domestic commercial flights had reached their destinations by early Tuesday afternoon, according to the FAA. Some airports also were evacuated.

"Anybody that is planning on going somewhere isn't going anywhere at least for now," said James Kerr, deputy director at Mitchell International Airport in Milwaukee.

Thousands of passengers gathered around TV sets at airports, staring silently at images of billowing smoke over Manhattan's skyline, flames shooting from Pentagon windows and people covered with soot running in the streets.

"I'm sitting here with shivers down my spine," said Dan Weiland, of Lewisville, Texas, an American Airlines passenger at Boston's Logan Airport. He said he called his children to reassure them.

Steve Hyatt, 55, of San Antonio, Texas, was stunned when he heard the news at Denver International Airport. "I just felt like I went into a trance and a dream," he said.

"It's going to be interesting to see what our country does in light of what took place with Pearl Harbor and comparing this to Pearl Harbor," he added. "But who do you fight, who do you get mad at?"

Around the nation, airports were put under heightened security.

Los Angeles International Airport and San Francisco International Airports were evacuated except for essential personnel, according to officials.

Boston's Logan International Airport -- the departure point for two of the doomed planes -- underwent a security sweep.

At Chicago's O'Hare International Airport, passengers were barred from entering the gated areas, and police patrolled with dogs.

At Seattle-Tacoma International Airport, concourses were closed and flights were canceled until 7 a.m. Wednesday. Denver's airport is closed for 24 hours, according to the media information line. The airport's concourses were evacuated and major roads to the airport were closed.

In New Orleans, passengers were not allowed into the airport, but it was not evacuated.

American Airlines initially said the Trade Center was hit by two of its planes, both hijacked, carrying a total of 156 people. But the airline later said that was unconfirmed. Two United airliners with a total of 110 aboard also crashed -- one outside Pittsburgh. The pilots union said a United plane had hit the Trade Center, but the airline did not confirm that.

Northwest, Continental and Delta Airlines said all their planes had been accounted for.

At Dallas-Fort Worth International Airport, hundreds of people were stranded and there were long lines at pay phones as families called friends and loved ones.

Rob Taylor, 32, of Colorado Springs, Colo., arrived at the Denver airport when he learned of the canceled flights.

"I was pretty shocked," he said. "I mean, it's turning into anger pretty quickly. I hope they take this as a final sign that they need to be a little more hard-handed and take the gloves off and go after these people."

June Locacio, 58, watched the scene on television in a standing-room-only bar at Lambert Airport in St. Louis. She heard the news after she got off a plane from Atlanta, Ga. as she was heading to Sioux Falls, S.D.

"It's absolutely stunning," she said. "I think it's an act of war. I can't believe they hit the Pentagon as well. ... I hope we're up to the task."

At the Hyatt Hotel in New Orleans, Kelly Lenox returned from the airport where she had been scheduled to fly home to St. Louis. She said security officers told her to leave the airport.

"You think you're safe, but you're not," she said. "Who would have thought the Pentagon ...." Her voice trailed off.

Lenox said she would rent a car to get home.