AND pressurized aircraft like airliners have a limited lifetime measured in pressurization cycles, not flight hours or any such calendar time. Every flight leg (takeoff/landing) counts against the 'lifetime' of the airframe. The airplane boneyards out west are full of airliners less than 20 years old - ones that have already reached their limit of pressurization cycles. Why? Remember when Aloha Airlines Flight 243 lost an entire section of cabin 'roof' a number of years ago (April 1988)? Too many pressurization cycles that caused microscopic cracks in the skin, which also allowed corrosion from the salt air to weaken further. The plane was only 19 years old.






Unpressurized aircraft generally have component lifetimes measured in flight hours, if they have such a limit at all. That's why we still have DC-3/C-47s flying commercial operations around the globe at 80+ years old!


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