BENTONVILLE, Ark. — John Walton, the billionaire son of Wal-Mart founder Sam Walton and a member of the company's board, died yesterday in a plane crash in Wyoming.

Walton, 58, of Jackson, Wyo., was piloting an ultralight that crashed shortly after takeoff from the Jackson Hole Airport in Grand Teton National Park, the company said. He was pronounced dead at the scene, and the cause of the afternoon crash was not known, officials said.

The plane was an experimental ultralight aircraft with a small, gasoline-powered engine and wings wrapped in fabric similar to heavy-duty sail cloth, officials said.

In March, Forbes magazine listed John Walton as No. 11 on its list of the world's richest people with a net worth of $18.2 billion. He was tied with his brother Jim, one spot behind his brother Rob, and just ahead of his sister, Alice, and his mother, Helen.

Walton joined the board of Wal-Mart Stores in 1992 but did not work for the company.

"We're sad that John Walton, who was well-known and much-loved in this valley, died doing something that he loved to do, which was fly aircraft," said Joan Anzelmo, a spokeswoman for Grand Teton National Park.

Anzelmo said officials notified the Federal Aviation Administration and National Transportation Safety Board.

Walton was an Army veteran who served with the Green Berets as a medic during the Vietnam War. He was awarded the Silver Star for saving the lives of several members of his unit while under enemy fire, according to the company. He attended the College of Wooster in Wooster, Ohio, and served as a board member of the Walton Family Foundation.

The company said Walton pursued a variety of business interests, including working as a crop duster in the 1970s and building boats in the 1980s. More recently, he had formed a holding company to oversee business interests.

Walton is also survived by his wife, Christy, and son, Luke.