What determines an aircraft's lifespan?

Just like any piece of machinery, each plane has an intended lifespan. However, treating anything with care ensures that its lifespan can be extended. This begs the question as to how long the aircraft of today can remain airworthy?

Classic planes still take to the sky

At airshows around the world, we see iconic vintage aircraft take the skies. These are labors of love for many aviation enthusiasts who spend hours tinkering with their beloved aircraft to keep them in the skies. While many vintage aircraft remain airworthy, why do we see jetliners lined up for retirement and destined for the scrap heap?

When delivered from the manufacturer, an aircraft has an intended lifespan, which is not measured in years but by pressurization cycles, which are when the aircraft's fuselage and wings are stressed. Given that an aircraft is joined together with many fasteners and rivets, over time, these can be stressed, and cracks will develop, leading to metal fatigue.

Airlines make a substantial investment when they purchase a new aircraft, and ensuring their lifespan is critical for the airline's balance sheet. For the world's leading airlines, understanding how long one of their aircraft can remain in service assists in future-proofing, planning, and overall operations. Ensuring that commercial aircraft have durability and longevity and can manage their maintenance effectively will give the airline a clear vision of what determines their lifespan.

Frequent maintenance and repairs take place

An aircraft's lifespan depends heavily on the airline's investment in maintenance and repair. Regular inspections are scheduled for aircraft to ensure routine servicing and follow the manufacturer's guidelines to ensure the aircraft can remain in its best operational condition.

Airlines have strict maintenance programs in place, which will see their aircraft frequently outlive the average lifespan. However, if the airline doesn't give the airplane enough attention, and it leads to neglect, they can see their investment retire early, and in the long run, cost the airline more money.

Aircraft manufacturers have a list of regular maintenance guidelines that airlines should follow, and if so, their aircraft can remain operating for many years. If these guidelines are followed, the average Boeing 747 should be able to last up to 25 years, while the smaller Boeing 737 is estimated to last around 20 years in the sky. The differences in the airline's longevity depend on differences in design, the materials used, intended usage, and climate conditions.

Usage patterns play a part in the overall lifespan of an aircraft.

Operational usage of an aircraft can affect its overall durability and lifespan. An example of this is when aircraft are used for many short-haul flights each day. This will lead to more takeoffs and landings, which will increase pressure on the aircraft and cause more wear and tear. Compared to long-haul flights, these take off and land less frequently. However, the pressure of flying at higher altitudes can take its toll.

The environment in which aircraft operate can also play a part. When aircraft are exposed to extreme weather conditions, cold temperatures (like flights to the Arctic) or extremely hot temperatures (like Australia's outback) can influence the aircraft's lifespan.

Exposure to high humidity levels will inject moisture into the aircraft's nooks and crannies, leading to erosion, and in general, harsh weather will affect exterior damage. If airlines are operating in these challenging environments, protective measures for maintenance are a must to mitigate these pressures on the aircraft.

Technology also plays a huge part in extending aircraft lifespans. Today, we are seeing continuous improvement in technology and advancements in materials and engineering that have assisted in extending aircraft lifespans. Today's generation of aircraft has innovations, such as corrosion-resistance materials, which will help reduce the chances of wear and tear.

Up to 90,000 flight cycles for the Boeing 737

Commercial aircraft are expected to last between 20 and 30 years in service, while some will last longer with heavier investment in maintenance and repairs. As noted, commercial aircraft have a lifespan recorded by flight cycles and flight hours. While the Boeing 747 could last in the sky for up to 25 years, this is estimated at around 90,000 flight hours. For Boeing 737 , however, the lifespan is around 90,000 flight cycles, or 55,000 flight hours.

Looking at Airbus, Emirates' most popular aircraft, the Airbus A380 , has an estimated lifespan of 25 years, or 60,000 flight hours. Meanwhile, the Airbus A320 , can last around 60,000 hours or 24,000 flight cycles.

The lifespan of commercial aircraft has continued to evolve over the decades, compared to the early days of aviation, when aircraft were built with simple materials and had limited operations for periods of around a decade.

Developments in aviation history

During the late 1950s and '60s, aircraft lifespans began to improve due to more reliable maintenance and new engine technologies. This saw the Boeing 707 and Douglas DC-8 defy the odds and remain in service for some time. In the 1980s, the introduction of composite materials and improved aerodynamics also improved aircraft functionality and lifespan, eventually leading to the Boeing 757 and Airbus A320 continuing to take to the skies for several decades.

Today, new aircraft benefit from the latest technology and advanced avionics, pushing the average lifespan of commercial jet aircraft to between 25 and 30 years. Some airlines still operate aircraft that are more than 30 years old. The evolution directly reflects the industry's ongoing commitment to improving reliability, efficiency, and safety to ensure that aircraft can sustain longer periods of operation.

What happens next?

While you can spend hundreds of thousands of dollars to keep an aircraft in the sky, there will still be an ultimate end to any plane's operational life. When this occurs, aircraft go through a multi-step process.

Aircraft retirement was exacerbated during the C.O.V.I.D.-.1.9 Pandemic when airlines looked to offload older aircraft from their fleets to improve liquidity. Retired aircraft are often sent to dry environments, like the Mojave Desert or Alice Springs, where they can be preserved and harvested for parts.

When an airline sends an aircraft for long-term storage, it could be for two main reasons: preservation to be brought back to life later, or disassembly and salvage for parts. When it is the latter, engines and avionics can be removed and refurbished for another aircraft.

Materials such as metals and composites can be recycled in a bid to reduce environmental impacts. Hazardous materials, like oils, are carefully disposed of, and then frequently we see the fuselages come back in a new life, such as hotels or even a McDonald's in New Zealand, as linked below!

While it is widely accepted that commercial aircraft will last between 20 and 30 years, these numbers will ultimately depend on how the aircraft is treated. While many may consider chronically aged aircraft to be unsafe, they can last significantly longer than expected if they undergo a rigorous maintenance program.

Oldest aircraft in the sky for the 'Big Three' US carriers

The three main airlines in the United States, namely American, Delta, and United, are often called the 'Big Three'. While these carriers have embarked on fleet renewal plans, they still have several retiring aircraft. With this in mind, what are the oldest aircraft still in operation for these carriers?

American Airlines

• N649AW - Airbus A320-200

Fort Worth-based American Airlines still has a 26-year-old Airbus A320 in its fleet. Inherited from US Airways in October 2015, the aircraft was first delivered to America West Airways in April 1998 and subsequently joined US Airways in November 2006. At the time of writing, Flightradar24 indicated that the aircraft would be based out of Phoenix, operating several domestic flights to St. Louis, Sacramento, and Fresno.

Delta Air Lines

• N649DL - Boeing 757-200

At 35 years old, this aircraft first entered service for Delta in May 1989 and is configured in a VIP configuration with 72 first class seats. The airline is expected to retire the aging aircraft within the next few years, as vast numbers of Airbus A321neos and Boeing 737 MAX 10s are delivered, serving as ideal replacements for the 757. According to Flightradar24, the aircraft was still busy at the time of writing, operating between Pittsburgh and Toronto, Milwaukee and Minneapolis, and Denver and Bedford.

United Airlines

• N641UA - Boeing 767-300ER

First delivered to United in April 1991, this 33-year-old bird continues to fly for the Star Alliance member. At the time of writing, the aircraft was scheduled to operate between Houston and Amsterdam, San Juan, and Geneva. The sub-fleet of 767s at United has an average age of almost 29 years old and is expected to be retired by 2030, to be replaced by the 150 787s that the carrier has on order.