Comment by shakna

That certainly might be one of the oldest Fortran codebases still in use I've heard of, but not quite the largest. (Character came in '77 wasn't it?)

E3SM [0] is still maintained today, and somewhere around 2mil LoC of F90.

Modern Fortran has a lot of niceties that it brings to the table.

[0] https://e3sm.atlassian.net/wiki/spaces/DOC/overview | https://github.com/E3SM-Project/E3SM