What is more impressive is how rare these events are, given the complexity of the underlying systems. Redundancy is not without its own problems (source of truth, for instance).
https://www.ft.com/content/65544730-8216-11e4-b9d0-00144feab...
And that's just the UK. Airport systems crashing is a regular occurrence. Paris crashed due to still relying on a Windows 3.1 system:
https://www.zdnet.com/article/a-23-year-old-windows-3-1-syst...
The IT is just poor. Tech firms routinely change much more massive and complex systems at a far faster pace compared to the stagnation found in airline IT, and yet total failures are not more frequent.
https://www.dw.com/en/lufthansa-system-failure-causes-massiv...
Though this is not due to outdated IT, but lack of redundancy of a critical component of the system instead.