How Long do Airplanes Typically Last? Are They Ever Declared Too Old?
Commercial airliners have a typical lifespan ranging from 20 to 30 years, but this longevity is not measured simply by the years since manufacture. Instead, the age of an aircraft is determined by a more accurate metric: the number of pressurization cycles.
Understanding the Pressurization Process and Metal Fatigue
The pressurization process is essential for maintaining a comfortable cabin environment during flights. However, it also subjects the aircraft to stress, leading to metal fatigue over time. This process can be compared to bending a paperclip repeatedly until it snaps. This demonstration highlights the risks of metal fatigue.
To illustrate, an aging Boeing 747 can endure approximately 35,000 pressurization cycles or accumulate around 135,000 to 165,000 flight hours before metal fatigue becomes a concern. It's important to note that modern planes using composite materials have not yet been affected by this issue, mitigating the risks associated with metal fatigue.
A Case in Point: The Aloha Airlines Incident
An unfortunate accident linked to metal fatigue occurred in 1988 when an Aloha Airlines Boeing 737, which had exceeded the safety limit with over 90,000 flight cycles, experienced an explosive decompression. Widespread metal fatigue cracks caused a portion of the aircraft's roof to tear off during a flight from Hilo to Honolulu, resulting in one fatality – a flight attendant who was sucked from the cabin.
Factors Influencing Aircraft Lifespan
The operational age of an aircraft varies based on the type and usage. For example, a long-range Boeing 787 flying daily for 12 hours is likely to remain in service for many more years than a short-haul Boeing 737 operating eight 2 to 3-hour flights daily.
Once a plane reaches an average age of 30 years and is considered too old, it is often retired to aircraft boneyards in the deserts or sent to scrapyards where it is disassembled for second-hand parts. Airlines sometimes highlight the average age of their fleet as a means of promoting their services, leading to comparisons like Indigo Airlines of India boasting an average fleet age of 3.57 years and Qantas maintaining an average age of 14.7 years.
Reliability Beyond Age
Contrary to common misconceptions, the age of an aircraft does not necessarily indicate a decline in reliability. The key factor is the airline's commitment to maintaining and repairing the aircraft properly. For instance, United Airlines, while boasting the oldest fleet among major US airlines with an average age of 16.2 years, continues to operate Boeing 767s that are between 30 and 32 years old. These planes have been maintained well and continue to operate safely and reliably.
Conclusion
While commercial airliners are designed to last for several decades, their continued operation depends on the number of pressurization cycles, not just the years since manufacture. Proper maintenance and good practices are crucial in ensuring that even older planes can remain safe and reliable in service.