Tradition is just as highly regarded as athletics at the Olympic Games, but Salt Lake City's spectacle will feature an unprecedented effort in the history of sport — a $310 million security system.

Nearly 16,000 security personnel — enough to give each athlete six bodyguards — are charged with making the games safe for athletes and the 1.5 million ticket holders.

Staffed by 59 agencies, the security force for the Games is comparable to the size of a major city police department. From helicopters and jets to high-tech surveillance devices, the Olympics are being guarded by a wide variety of security measures.

Yet despite the unprecedented security budget, technology and man-power, officials aren't making any promises the system is perfect.

"We may not eliminate risk entirely because there is no such thing as an absolute fail-safe guarantee in Salt Lake City or anywhere else," U.S. Homeland Security Director Tom Ridge said Thursday.

The opening ceremony will be the first test for this massive multi-layered security plan that is three years in the making.

President Bush, U.N. Secretary-General Kofi Annan and three other heads of state will join 55,000 fans and the world's best winter athletes in Rice-Eccles Stadium, on the University of Utah campus.

"There is no margin for error," Secret Service agent Mark Camillo said. "We don't get a second chance."

Sniper teams will be positioned on nearby roofs, Black Hawk helicopters will hover nearby, and all flights in and out of Salt Lake International Airport will be halted for four hours.

But cracks in the system have already been revealed.

The day before Friday's opening ceremony a bag that appeared to contain an explosive was discovered next to a parking garage near the downtown Olympic media center.

Although it was discovered to be just a bag of electrical wires and fuses, the swarming response by Olympic security underscored fears that it might have been a ruse designed to test the system.

"There's some concern it was like a trial run," Salt Lake Police City spokesman Craig Gleason said.

The Secret Service has employed everything from the latest technology for fighting bioterrorism to bomb-sniffing dogs that will make daily sweeps through Olympic venues in a sprawling 900-square-mile area, in the Salt Lake Valley and the nearby Wasatch Mountains.

Outside the stadium, spectators will stand in long lines waiting to get through metal detectors under the watchful eye of National Guardsmen carrying M-16s.

The horror of the Sept. 11 terrorist attacks convinced officials to create this pricey and prolific security system.

But IOC President Jacques Rogge said security plans didn't alter greatly because of Sept. 11 and won't necessarily be as tight as some past games. He noted the extreme precautions taken for the 1976 games in Montreal that followed the massacre of Israeli athletes at the Munich 1972 games as an example.

The bombing in Atlanta during the Summer Games in 1996 was also a wake-up call to officials to tighten Olympic security.

"The scenario of a plane crashing into a venue is a scenario that has been on the risk list for 15 years," he said. "Whether we have the means to prevent it is another issue, but there have been no-fly zones in all Olympic Games for the past decade, and there will be a no-fly zone in Salt Lake City."

Security planners have tried to keep much of the protection as unobtrusive as possible. Hundreds of police will look much like ordinary spectators mingling with crowds, and cameras will discreetly keep watch on all Olympic sites.

"All that can be done to make this a safe place has been done," Salt Lake Olympic chief Mitt Romney said. "This will be a safe place. I think you can make the argument this will be the safest place on Earth for 25 days."

Moving massive crowds quickly through security checks is just about the only thing not hammered out.

Every visitor to every event and venue will be scanned with a metal detector, a first for the Winter Games.

"We're absolutely ready to go," Secret Service spokesman Mark Connolly said. "We're looking forward for the focus to move to the games themselves, the athletes and competition and away from the security preparations."

It's hard to miss the National Guard, though, and a close look into the woods near the ski slopes will find agents walking through the snow.

That's fine with most athletes, who say they welcome the protection.

"The more F-16s I see flying around, the safer I feel," U.S. skier Picabo Street said.

And that type of reaction is just want officials want to hear.

"We want to take the concern of security away from the athletes so they can concentrate on performance," United States Olympic Committee CEO Lloyd Ward said.

Fox News' Amy Sims and The Associated Press contributed to this report.