Unhappy academic here - codebases with millions of lines of Fortran are very prevalent here as well. It is both better and worse than a lot of people think; like a lot of the other comments said, that code is rarely touched, but when you need to touching it can be very painful. Modifying old Fortran is rough, mostly because of that awful, awful IMPLICIT keyword. Though I will say that the native multidimensional array support does make certain sections much easier to read than corresponding vanilla C code.