Americans are slowly returning to the skies and while security remains tight and time-consuming, the federal government is allowing some airports to resume one timesaving measure: curbside check-in.

Air travel still is well below levels prior to the Sept. 11 terrorist attacks. Federal Aviation Administration spokesman William Shumann said airlines are flying 80 to 85 percent of their pre-attacks schedules.

But the Air Transport Association, a trade group for the major airlines, said preliminary estimates showed 665,714 passengers flew on domestic flights Thursday, compared to 518,765 the Thursday before. The flights were 46 percent full, up from 39 percent a week earlier.

A year ago, airplanes carried around 1 million passengers a day and were around 70 percent full.

There were no numbers on weekend flights, but airport and airline officials said it appeared more people were flying.

Bill DeCota, aviation director for the Port Authority of New York and New Jersey, which runs Kennedy, LaGuardia and Newark airports, visited all three facilities on Sunday and reported the terminals were busier.

Michael Wascom, spokesman for the airline trade group, said he flew into Baltimore from Pittsburgh on Sunday and the plane was full.

Monique Bond, a spokeswoman for the Chicago Department of Aviation, said there were longer lines at security checkpoints at both O'Hare and Midway airports.

"That's a good sign" Bond said. "Increased lines mean there are more travelers regaining their confidence in air travel."

President Bush and members of his Cabinet have been encouraging Americans to return to the skies, saying it will help boost the economy and return some normalcy to lives disrupted by the terrorist attacks.

Airline passengers are seeing greater security at airports and being encouraged to arrive two hours before departures. The National Guard has personnel patrolling major airports and more strenuous checks of passengers and baggage are being conducted everywhere.

Travelers at Los Angeles International Airport were forced to wait at shuttle depots and give up once-innocuous items such as nail files and clippers, but most took the new rules in stride.

"The added security gets you, but it's something that's necessary," said Bishop O.C. Coleman, 47, a New Orleans musician returning home after seeing his daughter perform at a concert in the San Francisco Bay area.

Some said they were a little nervous about flying again, and also saw the tension in their fellow passengers. "Children were crying and everybody looked a little afraid," said Kerri Kubrick, 32, who was waiting at Los Angeles airport for a ride home to San Diego after a trip to Norfolk, Va.

Los Angeles Airport spokeswoman Nancy Suey Castles said officials have received relatively few complaints about the new inconveniences, but some of those complaints have been "pretty vociferous."

"In the old days, if you went through the metal detector and if something beeped you could take something off and go through again," Houston Aviation Department spokesman Ernie DeSoto "Now you have to be checked with the magnetic wand and it takes a little bit more time."

At least three airports -- Dulles outside Washington, Houston's Bush Intercontinental and O'Hare in Chicago -- are allowing passengers of certain airlines to check their baggage at the curbs, albeit under stricter security procedures.

Curbside check-in was banned when airports reopened following the attacks. Shumann said the FAA now is approving requests from individual airlines and airports to allow curbside check-in if the tighter security measures are followed. He declined to identify the measures, citing security needs.

Meanwhile, former American Airlines Chairman Robert Crandall called for airline passenger reservations to be checked against law enforcement lists of potential terrorists. He said on CBS's "Face the Nation" that the airlines' reservation systems should be tied in with the FBI, CIA and other anti-terrorism intelligence agencies

Two of the terrorists who hijacked the four commercial airliners on Sept. 11, Khalid Almihdhar and Nawaf Alhazmi, were placed on a terrorist watch list this summer, but were already in the United States and were never picked up. This way, the airline could have alerted law enforcement authorities that they had bought tickets.

"What I think we need is an integrated security system from stem to stern," Crandall said.

Capt. Duane Woerth, president of the Air Line Pilots Association, said on CBS that all airports, including those that handle only cargo flights such as Federal Express or United Parcel Service, should have the same level of security as major passenger facilities.