Delta being down for four hours is not an issue of "systemic importance". Safety-related issues are already (and rightfully) publicly dissected, but it's hard to see what a post-mortem showing (what is likely to be) the interplay of a couple of subtle and individually benign problems which when hit by the power outage became a big issue will do much except enable a large chorus of armchair experts to pronounce on how this is obviously the fault of evil cost-cutting management/because they didn't use the cloud/because they used the cloud/fixed in the latest version of node.js.