Notwithstanding the other points, our "Air traffic Control Systems Consultant" has weird logic. We had major traffic delays because the computer fell over and we had to revert to a well tried and tested but lower capacity paper and pen system. Nobody crashed.
The answer to this situation apparently is a more complicated computer and no back up at all. That would be enough to keep me on the ground I can tell you!
I am a mere PPL/IMC with 35 years in IT and telecomms.