Look, up in the sky. It's a bird. ... It's a plane. .... No, it's a knucklehead!

The rumors are true.

Actor-comedian Bill Murray will parachute today from a Fokker 31-C at the 50th Chicago Air & Water Show.

The Wilmette native, who played a bumbling recruit in "Stripes," will take a dive at 3 p.m. with the Golden Knights, the U.S. Army Parachute Team. The Oscar nominee ("Lost in Translation"), in a black-and-gold jumpsuit, will train with the 12-member team earlier in the day, spokeswoman Donna Dixon said. He will perform a tandem jump with Staff Sgt. Joseph Jones.

Some guys write a check for charity. But Murray, 57, is taking the 13,500-foot-high pratfall on behalf of USO of Illinois, a nonprofit group that helps veterans. His "flight schedule" includes a 6,000-foot free-fall and a landing on North Avenue Beach.

It will be easy to pick out Murray, Dixon said. The diehard Cubs fan "will have the largest parachute in the sky. It will be four times the size of the parachutes the other jumpers have. ... I'm sure you'll be able to hear him hollering and screaming as he comes in," she added, jokingly. "He'll be phenomenal."

That's the fact, Jack.

Murray's feat will be immortalized by Knights-videographers Sgt. Joseph Ablen and Sgt. Bryan Schnell, the latter who jumped with former president George Bush on his 80th birthday in 2004.

The stunt will be preceded by TV mom Florence Henderson ("Brady Bunch") singing the national anthem. Actor Gary Sinise ("Forrest Gump") and the Lt. Dan Band will give a free concert at 5 p.m. at the North Avenue Beach Boathouse. Fireworks follow at 8:45 p.m. over Lake Michigan.

The nation's largest free show of its kind continues with extreme-water antics at 9 a.m. Saturday and Sunday. The air segments run from 11 a.m. to 4 p.m. both days. Jubilee headliners include the U.S. Navy Blue Angels and the Navy's Leap Frogs Parachute Team, the AeroShell Aerobatic Team, the Firebirds and Lima Lima Flight Team.

The F-22 Raptor, the Air Force's newest and most advanced fighter, is among the aircraft making a special appearance. The stealth fighter has made cameos in "Transformers" (2007) and "Iron Man" (2008). The expanded three-day air show is expected to draw more than 2 million to the lakefront this weekend.

Grapevine

British actor Simon Pegg ("Shaun of the Dead," "Hot Fuzz") hits town later this month to chat up his new comedy "How to Lose Friends & Alienate People." Pegg is slated to play Scotty in the next "Star Trek" film ... Lyric Opera is seeking three extras to play a detective, coroner and police officer in Gershwin's "Porgy and Bess." Report at 6 p.m. Aug. 20 to the Civic Opera House (the stage door entrance is at Washington and Wacker Drive). Call (312) 827-3538 for details ... Sounds like The Joynt is a bastion of next-generation talents. Jazz drummer Kendall Lewis (son of jazz great Ramsey Lewis) and his trio headline the Swing Bar on Fridays and Saturdays while singer Shirley King (B.B. King's daughter) performs Wednesdays at the River North club.