By the spring of 1999. Frye recalls, "Enterprise Systems Group General Manager William Zeitler had enough information for a final chart of his presentation to then-CEO Lou Gerstner: ‘We also have Linux on s/390,’ Zeitler said." Gerstner was not impressed at first. In fact, "’That’s the stupidest idea I’ve ever heard,’ said Gerstner, who then paused for reflection and added ‘Or maybe not?’"
Original source: 20 years of Linux on Big Iron