In the mid 80s I did a lot of assembly programming on ACP for KLM. We (125 programmers and me) shared a test system that boasted 128MB RAM and a 100MHz'ish CPU running ACP/TPF. The production system even had double the memory. It could do 100 transactions per second. Touroperators (KLM representatives) all over the world used reservation terminals connected by satellite lines to this mainframe. It definitely was mission critical. But I think the article exaggerates a bit, because internally the story was that the KLM would go broke if the mainframe went down for three consecutive days.
When I was there, C was being tested as an alternative for assembly language, but it was thrown out, because it was too slow, and wasted too many resources.
Mind you: my iPhone has more CPU and much more memory than this mainframe, and thus could easily run the entire worldwide reservation system for an medium sized airline!