Comment by nunez

I completely believe it. The critical paths in critical software operated by every major company or governmental entity that you deal with were written in COBOL/Fortran/Progress and run on IBM mainframes (hence why they are still a tech titan and will probably remain so for the foreseeable future). And they aren't moving away any time soon because they are too important to fail.

Things that are largely or entirely done on mainframes today:

- Airlines: ticket reservations, crew management, route planning, critical flight operations, some parts of traffic control

- Banking: money movement, loan origination (though some of this has moved off over the years), account management (most of the slick frontends you use on the daily are just wrappers around mainframe programs)

- Government: So much state government stuff (licenses/registrations, tax systems)

I haven't personally done a lot of work on the mainframe, but as I understand it, they are still unbelievably robust machines that are extremely redundant and reliable and still have unmatched uptime guarantees.