John T. Walton, who as an heir to the Wal-Mart Stores Inc. retail fortune was ranked as one of the world's richest people, died yesterday in Grand Teton National Park when the ultralight airplane he was flying crashed. He was 58.

Mr. Walton, whose wealth was placed in the many billions of dollars, was a philanthropist, a decorated Vietnam veteran and an experienced aviator who once worked as a crop-duster.

He once told an author why he had been reluctant to make a career in the enterprise founded by his late father, Sam Walton.

"You never really know whether you're getting a job because of who you are or whether you earned it," he was quoted as saying in a 1990 book by Vance H. Trimble.

Mr. Walton was a product of public schools and had starred in football in high school in Bentonville, Ark., the headquarters of Wal-Mart, the nation's dominant retailer.

He dropped out of the College of Wooster, in Ohio, after two years and joined the Army, attaining the rank of sergeant in the Special Forces and winning the Silver Star.

After his return, according to a book by Bob Ortega, he learned to fly and went to work as a pilot for Wal-Mart, but he soon left to fly crop-dusters over the cotton fields of several southern states, eventually creating a thriving business.

A sky diver and a scuba diver, he later moved to San Diego, where he founded a company that built trimaran sailboats.

Sam Walton, who opened his first discount store in Rogers, Ark., in 1962, died in 1992. Based on his stock holdings, John Walton, a member of Wal-Mart's board, was listed by Forbes magazine this year as the world's 11th-richest person, with $18.2 billion.

He had been described as a venture capitalist and the guiding figure in the family's charitable giving, much of which goes to educational programs, and was a co-founder of the Children's Scholarship Fund, which helps needy grade-school students afford private school tuition.

His plane crashed almost immediately after taking off from Jackson Hole Airport in Wyoming, said park spokeswoman Joan Anzelmo.

The cause was being investigated, she said.

Survivors include his wife, Christy Walton; his son, Luke Walton; his mother; two brothers; and a sister.