ATLANTIC CITY - For years it was among the best-kept secrets of the Atlantic City Airshow: Go to the city a day early and watch the practice session - nearly the same show - without fighting traffic jams and crowded beaches.

In recent years, however, it has become less of a secret as more and more spectators gather early on the beaches in Atlantic City, Brigantine and Ventnor to watch everything from aerial acrobatics to rescue demonstrations.

That's just fine with show organizers and local promoters, who say many of the people who watch the practice stay overnight, making the city a multiday destination.

Bringing in crowds over multiple days has become more of a priority than ever this year, with the addition of the inaugural Atlantic City Salutes America's Armed Forces Parade on Monday, which organizers predicted would capture the early attention of airshow crowds expected to be as large as 750,000.

This year's practice session takes place from 10:30 a.m. to 4 p.m. today - just one hour shorter than Wednesday's show. Participating acts follow about the same schedule on practice day and show day.

"People have caught on to the secret that dress rehearsal is just that. They're going to see a great show with fewer crowds," Atlantic City Convention & Visitors Authority Executive Director Jeff Vassar said. "It makes it more attractive, and it keeps them in the city longer."

The ACCVA gathers anecdotal information about spectator habits. Vassar said they agency has learned that some people arrive in town Tuesday to watch half the show without the crowds, but then return Wednesday morning to get a taste of the excitement.

Practice has become so popular that some venues have generated their own events based around the dress rehearsal, such as the party at The Rooftop Pool at Caesars Atlantic City from noon to 4 p.m. today.

Practice means safety

David Schultz, the air boss who has run the show since its return to Atlantic City in 2004, stressed that while practice day is fun for the crowds, it's also necessary for the pilots. Practice gives the pilots a chance to get better acquainted with the airspace.

Because the show takes place over the ocean, pilots look to piers and boats stationed throughout the water to keep their bearings rather than the usual runways and buildings used as markers at shows over airports and other land-based venues.

Not all acts participate in practice, and the booming announcements of the aircraft and performance groups via loudspeakers will be missing. Still, about 70 percent of the show can be seen today. The acts that do not participate are handling less-complicated flyby maneuvers, Schultz said.

Some secrets will still remain on show day. At about 1 p.m. Wednesday, spectators can expect a surprise appearance by an undisclosed act, said Schultz, who declined to release any additional information about the act other than to say it's something that's never been seen during Thunder Over the Boardwalk.

"Don't just expect to see acts coming in from the left and the right. They'll come from all over the place," Schultz said, adding that the show is timed to have an act fly by nearly every minute. "We'll keep the crowd's heads on a swivel for six hours."

Contact Jennifer Bogdan