In a sort of senior-citizen version of "Fear Factor," former President George H. W. Bush (search) plans to celebrate his 80th birthday by jumping out of a plane Sunday at 13,000 feet.

"A scary feeling," Bush said in his usual pronoun-free style as he contemplated standing in the open door of the plane with a parachute on. "A funny feeling in your tummy or your knees."

Bush has made four parachute jumps in his life - three since leaving the White House more than a decade ago, including one on his 75th birthday.

"People say: 'Why are you doing this, you nutty old man?'" Bush said. "I say: One, because I want to. It feels good. There's a thrill involved. And two: Just because you're 80 doesn't mean you're finished. It sends a message to a lot of people ... that old age is not a barrier."

This jump will be much different from the first time Bush bailed out of a plane. That was in 1944, when the 20-year-old Navy pilot was shot down over the Pacific.

Bush, who talked to The Associated Press last month about the skydive, decided to go ahead with the jump despite the death of President Reagan.

The Bush family will attend a memorial service for Reagan in Washington on Friday, then travel to Texas on Saturday, Bush's birthday, for a party at Houston's Minute Maid Park (search) with son George W. Bush, former Soviet leader Mikhail Gorbachev, former British Prime Minister John Major and 5,000 other invited guests. The entertainment will include Vince Gill, Amy Grant, Tommy Tune, Bo Derek and Dennis Miller.

The party serves as a fund-raiser for the George Bush Forty-One Endowment (search), which is trying to raise $30 million to support his presidential library, the University of Texas M.D. Anderson Cancer Center and his Points of Light Foundation (search). Tickets start at $200.

"Given the charitable nature of these events, we believe President Reagan would be the first to say, `The show must go on,'" Bush spokesman Jim McGrath said.

On Sunday, many of the partygoers will take a 100-mile train ride from Houston to the Texas A&M campus in College Station, where Bush, as he did during his last jump five years ago, will bail out over his presidential library.

"The view is really unbelievable," he said. "It's really hard to describe. The most tranquil part, for me the most wonderful part, is when you're floating alone down to earth. It's total quiet ... peace, total peace."

But not total solitude. An Army parachute team, the Golden Knights (search), will accompany him.

To get ready Sunday morning, Bush will talk with the folks he will jump with and go over the plan one more time. He will also do one other important thing: "Thanking the guy who packed the parachute," he said.