Language for the ages

Here's an interesting problem. Suppose you wanted to write an application for a manufacturing process that will, in all probability, run for the next 30 years. No direct control of the process itself is entailed (i.e., you don't need the program to operation valves or run motors), but you do need this program to compute manufacturing parameters for each customer. I/O requirements are very modest, mostly simple keyboard and display. What would you write it in? Clearly, you'd want to be independent of a particular software vendor, so the likes of Visual BASIC isn't an option. You'd also want to write in a language that isn't nearing obsolescence, nor one that's still evolving. "Niche" languages would be out of the question, as longevity could be a problem. So what would it be? My vote is for FORTRAN.