Most are - irony of irony is that when Delta had its big outage due to CrowdStrike, dealtamatic/deltaterm was still running just fine, but no one could get into it because all of their windows machines were locked out.
At the core of most airlines is a customized version of IBM TPF, its very reliable and highly available, its all of the other stuff that breaks down.
We will in time find out what grounded AS, I wouldnt be surprised if its some sort of middleware connecting their iPads to the CRS they use for ticketing operations, but it could also be something as simple as their weight and balance application going offline.
AS is a fairly well run airline (as are DL, AA and UA) with a heterogeneous mix of systems in service, ideally this heterogeneous nature should make for a more resilient system but it also can lead to single points of failure when you have to glue too many different systems together.
