Fifty years after he founded the company, Frederick Smith announced on Monday that he will step down as FedEx’s chief executive in June. Raj Subramaniam, the current president and chief operating officer, will succeed Smith, according to a news release from FedEx.

“FedEx has changed the world by connecting people and possibilities for the last 50 years,” Smith, 77, said in a statement on the company’s website. “As we look toward to what’s next, I have a great sense of satisfaction.”

A former Marine officer who served two tours of duty in Vietnam, Smith came up with the idea for FedEx from a term paper he wrote in 1965 while he was an undergraduate at Yale University.

The paper, which explained how companies could deliver items faster if they changed their shipping strategies, was given a C grade because Smith’s professor didn’t think the strategy was viable, according to Entrepreneur Magazine.