The first few jetliners returned to the nation's skies Thursday, but several major airports remained closed and others opened only briefly. The few nervous passengers who did travel faced strict new security measures following the terrorist attacks in New York and Washington.
There was tension and confusion as the aviation industry inched back into service for the first time in two days.
The New York area's three major airports Kennedy, LaGuardia and Newark, N.J. were opened and then abruptly shut down as FBI officials detained several people for questioning in the attacks. Police said a man carrying a false pilot's identification was arrested at Kennedy after trying to get past security.
Earlier, Orlando International Airport and a terminal at LaGuardia were briefly evacuated over separate, unfounded bomb scares. And after briefly resuming limited service, Northwest Airlines canceled all flights Thursday evening after receiving information a spokeswoman said indicated it was "not prudent to operate." No other details were released.
By late afternoon, about 250 commercial airline flights were traveling in U.S. air space, the Federal Aviation Administration said. On a normal Thursday, about 6,000 flights would be in the air, including military and private planes.
Elsewhere, no planes had left Chicago's busy O'Hare International Airport by evening and authorities said Washington's Reagan National Airport, near many of the capital's landmarks, would remain closed indefinitely.
FAA Administrator Jane Garvey told reporters that Boston's Logan airport would not be reopened until new stricter safety measures are in place. The airport is under investigation for possible security breaches before the attacks.
Despite all the confusion, travelers for the first time since Tuesday had the option of flying in the United States even if the service was limited to a handful of flights.
At Sky Harbor International Airport in Phoenix, Sam Hemphill was among a dozen people lined up at a TWA ticket counter. He said he was uneasy about flying but wanted to get home to Jacksonville, Fla.
"Whatever happens, happens," Hemphill said. "You have to keep going. If you stop living life, they've won."
Lisa Adamson of Vancouver, Wash., was among the passengers on the first commercial flight to leave Portland, Ore., since Tuesday a Delta jet headed for Kansas City, Mo.
"I feel nervous," she said. People at the food court cheered as the jet took off.
Transportation Secretary Norman Mineta cleared the way for commercial flights to resume Thursday, saying airports would be opened and flights resumed on a case-by-case basis but only after the new security measures are in place. Private flights are still banned.
Under the tightest airport security since the Persian Gulf War in 1991, there will be no more curbside check-ins or visits to terminal gates to meet passengers.
Knives and other cutting tools, even plastic ones, are prohibited. Mail and cargo are temporarily banned from passenger flights.
Federal marshals were on hand at many airports.
"People in this country have a hang-up about having their personal space invaded, but when you're in this situation you have to sacrifice some of your individuality," said Kevin McArthur, a business consultant waiting at Denver International Airport for a flight to Chicago.
In Phoenix, three Northwest Airlines employees intentionally breached a security, carrying a small knife and a corkscrew past a checkpoint to show that security gaps still exist.
At Dulles, domestic flights took off Thursday evening amid a visibly increased police presence.
"I'm four days late going home, but that's better than what happened to a lot of people," said Burt Bates, a lawyer from Kansas City waiting to board a flight on Midwest Express. "Under the circumstances, it's very insignificant."