Safer skies? Aviation security remains under scrutiny.

Aviation security, measures adopted since 9/11 have not significantly made passengers safer or have been cost effective, experts contend. They also noted that many weaknesses in the previous system remain, despite billions of dollars being spent to enhance air safety.

In a report released earlier this year, Robert Poole, director of transportation studies at Reason Public Policy Institute, wrote that there are three basic flaws in the country's aviation security system:

It assumes all air travelers are likely to be a threat; it operates in a highly centralized, one-size-fits-all manner, and it is overseen by an entity that functions as both airport security policymaker and regulator as well as provider of some airport security services.

Costly screening technologies and other expensive measures are not making the skies any safer, contends Poole.

That assessment of the system is a striking contrast to what Transportation Security Administration Assistant Secretary Kip Hawley told the Senate Committee on Commerce, Science and Transportation just a few months ago.

"We are orders of magnitude beyond where we stood on 9/11 in securing aviation travel," Hawley said.

Poole said, "We have dealt pretty effectively with one big threat, and that is the threat of planes being taken over and being turned into suicide bombs ... but it has nothing to do with airport screening, which is where the bulk of the money continues to go."

Congress created the TSA shortly after 9/11 to help protect the nation from future terrorist attacks. The mandate for screening all checked baggage for explosives arrived simultaneously and the TSA spent billions of dollars to meet that goal.

According to a Government Accountability Office report, the TSA procured and installed 1,200 explosive detection systems, costing an average of $l million each, and about 6,000 explosive trace detection systems, costing an average of $40,000 each, between November 2001 and September 2004. However, because most airports could not accommodate the new machines in their underground baggage facilities without substantial upgrades and renovations, the TSA developed interim lobby screening solutions rather than installing more permanent in-line baggage screening systems.

"The baggage screening process is unnecessarily, hugely labor intensive," said Poole.

In facilities lacking an automated conveyor belt screening system, each bag must be physically carried to stand-alone machines. Not only does it cost more money to staff these machines, but the process is less efficient.

"The number of checked bags screened per hour could more than double when EDS machines were placed inline versus being used in a stand-alone mode," said the GAO.

Any airport, if given the funds to invest in automation, would do it in a heartbeat, said Poole. If the TSA focused solely on policymaking and oversight, and allowed airports to take over responsibility for implementing security measures, "we'd save close to a billion dollars a year on screening costs," he added. The savings could then be used to beef up other aspects of airport security, he said.

Analysts and the TSA have acknowledged that the biggest threat to aviation security is the use of explosives.

But Poole argued that the TSA is not "taking that threat seriously." For example, unlike their checked counterparts, all carry-on luggage are not required to be examined for explosives.

"It makes zero sense to exempt carry-on bags from that," said Poole.

Under the current screening protocol, carry-on bags proceed through x-ray machines. If any prohibited items are detected, the bags are pulled aside and the items confiscated. A portion of carry-on bags also is selected randomly for secondary inspections, which often include swabbing for traces of explosives residue.

Passengers too pose a risk, Poole pointed out. The vast majority of passengers pass through only metal detectors at security checkpoints, he said. Explosives typically are not made of metal and could be concealed under clothing. Those randomly selected for secondary, screenings are wanded or patted down and sometimes swabbed for explosives. To close that potential loophole and nab potential terrorists, the TSA has implemented a more thorough pat-down procedure and has deployed new portals that screen passengers for traces of explosives.

Another security vulnerability is that explosives potentially could be transported via the numerous ramp areas of an airport, said Poole. Thousands of people have access to those and they could be part of a terror organization, he said.

"They have a number of opportunities to put explosives on a plane," he said, and there doesn't seem to be a serious on-going effort to stop them.

"I look at billions being spent on passenger screening and practically nothing on access control, or controlling the perimeters of airports," said Poole.

One possible solution utilizes a technology that has been around for years: closed circuit television.

Most airports have security cameras in place with a central command center that monitors all the footage on multiple banks of television screens. Praetorian, a surveillance software application from L-3 Communications, stitches together those disparate scenes to create a three-dimensional environment on a single screen--similar to what one sees in a first-person shooter video game--which allows an operator to navigate a large area without having to flip through hundreds of static shots.

The system has been installed at the Jacksonville International Airport in Florida, where security officials "flew" through stored footage to track down a stolen cell phone minutes after the theft was reported.

Praetorian is designed so that it can link together numerous sensors, such as infrared cameras and motion detectors, and be programmed to alert operators to left-behind items or intrusions into secure areas.

"If someone came through security the wrong way, and the detection capability picked that up and quickly followed them down the terminal to see where they're at ... they don't have to shut down the whole airport anymore" to track down the culprit, said Corby Lawrence, director of business development for Praetorian.

L-3 also has a variety of hand-held thermal devices that could be handy for security units patrolling an airport by car, said Sharon Roberts, marketing manager for the company's infrared products.

"One of the benefits of thermal imaging is that people in a vehicle will glow--they can't fade into the background. It also gives you the ability to see through weather situations, such as rain, fog, snow, smoke, haze, etc. A lot of times, at airports, that would be a concern," she added.

The TSA is implementing changes to make the aviation security system more risk-based and the security measures less predictable.

"Whether you were a frequent flyer or a potential terrorist, you knew what to expect at the airport. With the changes we are implementing, that predictability will be gone," said Hawley.

Programs such as Registered Traveler will help agents filter past the harmless frequent fliers who volunteer to be rigorously screened for security checkpoint privileges and hone in on those passengers who haven't been cleared.

"You're talking about a potentially enormous workload being relieved," said Poole. To streamline the process further, he said, would require a real-time federal watch list, which does not yet exist.

TSA is working on a passenger pre-screening program called Secure Flight, that would match passenger information against terrorist watch lists to identify people who should undergo additional screening for domestic flights. That task is currently the responsibility of individual air carriers.

The program has come under fire for privacy issues and the GAO recently released a report that concluded, "significant challenges remain in developing and implementing the Secure Flight program."

At the Senate committee hearing, Hawley explained that the TSA is "re-baselining" the program to ensure best practices in management, security and operations.

"We will move forward with the Secure Flight program as expeditiously as possible, but in view of our need to establish trust with all of our stakeholders on the security and privacy of our systems and data, my priority is to ensure that we do it right, not just that we do it quickly."

The Registered Traveler program, on the other hand, is set to launch this summer.