Wal-Mart heir John Walton died Monday when his ultra-light aircraft crashed after taking off from an airport in Jackson, Wyoming, the company announced. Walton, 58, was the second son of Wal-Mart founder Sam Walton and served on the board of directors of the world's largest retailer. He was ranked No. 7 on the Forbes magazine list of the 400 wealthiest Americans in 2004, with a fortune estimated at $20 billion. A report of CNN said Wal-Mart has stores in the United States, Britain and Central and South America. Walton died when his plane crashed shortly after takeoff from Jackson Hole Airport shortly after 12:15 p.m. (2:15 p.m. ET), said Joan Anzelmo, a spokeswoman for Grand Teton National Park. The airport, which serves the resort town of Jackson and the surrounding area, is on the park grounds.