Originally Posted by MSPeconomist

also wouldn't worry about the airworthiness of these old birds as they were alway lovingly maintained by PMNW. I would assume (but do not know the technical rules) that when an aircraft is put back into service in such cases, a rigorous mechanical inspection is required. For example, even if an aircraft is parked over 24 hours for whatever reason, I know that some sort of inspection is required before it can be flown, at least for a commercial flight with passengers (versus a ferry flight, which might be an expection).