The time-critical parts of a hospital's workflow are less IT-dependent than the time-critical parts of an airline's workflow. You need a computer to handle admissions in hospitals, but you can get by with the actual medicine with the computers offline (there's a LOT of paper replication).

Besides, if $CLOUD_PROVIDER has a couple of hours outage and the patient records aren't available, not that much backs up. There's not that much in the count of patients that's affected by, say, a 2-hour outage. But that same length of outage can affect thousands of passengers across a dozen airports, and cause knock-on effects for days.