Between Christmas and New Year's, almost 9 million Americans will take to the skies for holiday travel - the highest number ever, even surpassing the nation's pre-Sept. 11 peak.
At the same time, they'll also be flying in the most secure skies ever. While several huge gaps remain in protecting the nation's aviation system from terrorists - such as the lack of proper screening for cargo and the continuing failure to have a single, authoritative watch list - even critics admit that great strides have been made since 19 young Arab men boarded four jets armed with box cutters and killer intentions in September 2001.
A myriad of things have changed, from the strength of cockpit doors to the attitude of flight crews. Prior to the Sept. 11 attacks, they were trained not to challenge hijackers. That was just one of many "glaring vulnerabilities" identified by the 9/11 commission.
Many of the recommendations made by the commission either have been implemented - like improved detection of explosives at checkpoints - or are being implemented - like the development of biometric identifiers for passengers and airport workers. They're part of what the Transportation Security Administration (TSA) refers to as its "many-layered approach" to fortifying the skies, an approach that recognizes no system is perfect.
"I don't think we can ever design a system that's going to be totally foolproof," says Richard Gritta, an aviation expert at the University of Portland in Oregon. "The TSA has made some good strides, but there's much more to do and there will always be human error. The flying public will simply have to get used to it."
Indeed just last week, baggage screeners at Newark Liberty Airport lost track of a fake bomb that had been used in a training exercise. The bomb look-alike was made of simulated Semtex, wiring, a clock, and a detonator. It was contained in a black bag that was put through a baggage screening machine and properly identified, according to a source at the TSA. But afterward, it was left with other passenger bags near a conveyor belt, and eventually it was loaded onto a flight to Amsterdam.
The TSA is investigating how the mishap occurred and says it will take appropriate action against the individuals involved. It also insists that at no time did the fake bomb present any threat to the public.
"It was a mistake made in training, and we'll be able to take the lessons learned and implement them in training procedures as we move forward," says TSA spokeswoman Amy von Walter.
But critics of the TSA see the incident as yet another example of the agency's failure to put enough emphasis on human training while at the same time relying too much on technology. The baggage screening machine worked; it was human error that caused the mishap.
"At the end of the day, the threats are human, and so it's a human process, a human action that's going to defeat these guys from doing what they want to do," says Andrew Thomas, an aviation security expert at the University of Akron in Ohio. "There's not enough training going on."
The TSA disagrees with that assessment, noting that security screeners get 100 hours of training before they start and are required to undergo at least three hours of on-the-job training every week. It was during such a training exercise that things went awry in Newark.
"We've provided more autonomy to local offices ... so they have more involvement in the training process," says Ms. Von Walter. "Unfortunately, in this case the [fake bomb] was mishandled."
Professor Thomas contends that far more widespread training is needed, and not just for screeners, but for flight crews as well. He notes, for instance, that it was a flight attendant who stopped shoe-bomber Richard Reid from lighting his explosive footgear.
Thomas advocates mandatory security and self-defense training for all pilots and flight attendants. This month the TSA launched a voluntary self-defense training class for flight attendants in five locations. It has also started a voluntary program to train pilots to carry firearms.
But critics, including many union members, believe that such training, particularly for flight attendants, should be mandatory.
"They have to work as a team. If one person is trained and the other people are not, you're really not improving security," says Christopher Witkowski, director of the air-safety health and security department of the association of flight attendants in Washington. "The pilots are locked in the cockpit now. They can't come out. The flight attendants are responsible for what goes on in that cabin, and there aren't air marshals on every flight."
Flight attendants are continuing to fight to make such training mandatory.
Despite the other improvements that have been made over the past few years, many security experts believe that terrorists continue to target the aviation system.
"There's a sense of urgency about what we have to do today to protect commercial air travel and, for that matter, all modes of transportation," says Doug Wills of the Air Transport Association, the major carriers' lobbying arm. "We realize that we can't eliminate all risk. We can only reduce it, and we'll only get better by trying different things to see what works well and trying to fix those that don't."