A security effort unprecedented in the history of sports paid off Friday as the Olympics opened without a hitch to the relief of spectators and organizers.

Thousands of security personnel, including snipers, prowled the grounds protecting a packed stadium including President Bush and world-renowned athletes.

Most of the 2,500 athletes didn't need to be convinced by top officials, who said the games would be safer than any — they came and proudly marched with the flags of their countries.

"It's like when I crawl in bed at night and I have my down comforter," said Nina Kemppel, a U.S. cross-country skier and four-time Olympian. "It's that same kind of comfortable, fuzzy feeling."

Even the anticipated long wait times and maddening lines to get into the spectacle didn't materialize.

Lines flowed better than expected and the stadium was filled long before the opening ceremony began.

"We're all breathing freely now," Salt Lake Olympic chief Mitt Romney said.

After three years of planning and a $310 million investment, security organizers were almost as eager to get the Olympics underway as were the athletes who crowded into the stadium.

The closest thing to a disruptive incident took place before the ceremonies when a group of protesters failed to disperse out of an area where Bush was to travel by. Five were arrested, but they were hardly considered a threat.

"It looks like they wanted to be arrested to make a point," Olympic security spokesman Marty Slack said.

Although no credible threat has surfaced against these games, top administration officials have warned that the Olympics could be a prime target of terrorists.

They also expressed confidence that a complex plan that includes 59 agencies and employs 16,000 security workers would protect the games.

It began for real Friday with a ban on all air travel in and out of the city's airport during the opening ceremony. A total of 332 flights were rescheduled or canceled during a four-hour period from 6-10 p.m.

Flight restrictions took effect at midnight Thursday for a 90-mile wide area over Salt Lake City for the remainder of the Olympics. Until the games are over, only commercial airliners and planes that go through security checks at four gateway airports in other states will be allowed through the airspace.

At the stadium, the security force was busy for hours before the ceremony, and a maze of fences and checkpoints stretched up to a half mile from its perimeter.

Police patrolled the fences on all-terrain vehicles, while helicopters kept watch overhead. The adjacent University of Utah campus, usually bustling with activity, was nearly deserted.

The Associated Press contributed to this report.