I wasn't comparing uptime needs of a hospital versus an airline, but their security needs.

Every major cloud provide offers multiple independent regions, and I haven't heard of any suffering from a multi-region outage.

If an airline's application can't tolerate an outage, then they better not host it in a single region, whether they host it themselves or host it in the cloud.

Delta is on day 2 of their outage, Southwest's was 12+ hours.

Google had a major outage in April -- it lasted 18 minutes. In June, AWS lost a single Availability Zone (out of 3) in Sydney for about 12 hours.