The Hidden Aftermarket Boom

By Alex Kulinsky, June 2026

For more than a decade, airlines built their fleet plans around a relatively simple assumption: new-generation aircraft would arrive on time, or at least close enough to plan. The Airbus A320neo family, Boeing 737 MAX, Boeing 787, Airbus A350 and other fuel-efficient platforms were expected to replace older aircraft, reduce fuel burn, lower maintenance exposure, improve reliability and support network growth. In theory, fleet renewal would be the main lever for lowering unit cost.

That assumption has become much harder to defend.

The global commercial aircraft market is now defined by a structural imbalance between demand for new aircraft and the industry’s ability to deliver them. Airbus and Boeing both continue to hold very large order books. Airbus ended 2025 with a record backlog of 8,754 commercial aircraft and delivered 793 aircraft during the year, while Boeing delivered 600 commercial aircraft in 2025 and reported more than 6,100 commercial aircraft in its backlog. At the industry level, IATA has highlighted that the worldwide commercial aircraft backlog reached more than 17,000 aircraft, while deliveries in 2024 were only 1,254 aircraft, around 30% below pre-COVID peaks.

This is not a temporary scheduling inconvenience. It is a major economic force reshaping airline operations, spare parts demand, aircraft retirement decisions, engine maintenance, used serviceable material, leasing markets and the global MRO sector. When new aircraft do not arrive, airlines do not simply cancel flights and wait. They keep older aircraft flying. They extend leases. They defer retirements. They buy more spares. They send engines and landing gears into shops more often. They invest in structural inspections, corrosion prevention, cabin refreshes and reliability improvements on aircraft that, under normal fleet planning, might already have left the active fleet.

In other words, aircraft delivery delays are creating an aftermarket super-cycle.

From Fleet Renewal to Fleet Extension

In normal conditions, an airline’s fleet plan is built around a balance between growth, replacement and retirement. New aircraft are introduced for three main reasons. First, they provide additional capacity. Second, they replace older, less efficient aircraft. Third, they allow the airline to standardize its fleet and reduce maintenance complexity.

When deliveries are delayed, all three objectives are disrupted.

An airline expecting ten new aircraft in a given year may have already planned new routes, higher frequencies, lower fuel consumption and the retirement of older aircraft. If only five aircraft arrive, the missing capacity must be replaced somehow. The airline may extend leases on older aircraft, bring parked aircraft back into operation, wet-lease capacity, reduce growth, or pay higher rates for available aircraft in the leasing market. Each option has a cost.

IATA estimates that aerospace supply chain challenges will cost airlines more than USD 11 billion in 2025. The largest elements include around USD 4.2 billion in delayed fuel savings, USD 3.1 billion in additional maintenance costs, USD 2.6 billion in excess engine leasing costs and USD 1.4 billion in surplus inventory holding costs. These figures show that delayed deliveries are not only a manufacturer problem. They directly hit airline profit and loss statements.

The logic is straightforward. A new aircraft normally comes with lower fuel burn, warranty coverage, better dispatch reliability and fewer heavy maintenance surprises in its early life. An older aircraft may be fully safe and airworthy, but it requires more work to keep it operational. As more aircraft remain in service beyond their originally planned retirement dates, the market sees higher consumption of parts, more shop visits and more demand for engineering support.

This is especially important for aircraft above 20–25 years of age. Age itself does not make an aircraft unsafe. Commercial aircraft are maintained according to approved maintenance programs, airworthiness directives and structural inspection requirements. However, older aircraft accumulate more flight cycles, more pressurization cycles, more repairs, more modifications and more corrosion exposure. Their technical history becomes more complex. The cost of proving continued airworthiness increases.

EASA’s ageing aircraft structure rule specifically addresses risks such as fatigue, widespread fatigue damage, corrosion, fatigue of repairs and continued operation with unsafe levels of fatigue cracking. The rule requires design approval holders and operators to support continued structural integrity programs and to revise maintenance programs where needed. In the United States, FAA supplemental inspection requirements similarly require damage-tolerance-based inspections and procedures for aircraft structures susceptible to fatigue cracking.

This regulatory framework explains why old aircraft can continue flying safely — but also why keeping them flying is not cheap.

New Parts: Higher Demand, Longer Lead Times and Less Warranty Protection

One of the first effects of delayed aircraft deliveries is increased demand for new spare parts. Airlines operating older fleets consume more components, more expendables and more structural parts than they would if they were replacing aircraft on schedule. At the same time, OEMs and Tier 1 suppliers are under pressure to support both production lines and the aftermarket.

This creates a difficult allocation problem. A supplier producing avionics, actuators, valves, sensors, pumps, flight control components or structural assemblies must support aircraft production, warranty obligations and spare parts orders. When the whole supply chain is constrained, aftermarket customers can face longer lead times and higher prices.

The warranty effect is also important. New aircraft are typically covered by manufacturer and supplier warranties for defined periods and conditions. That does not mean the aircraft is free to operate, but it does reduce some early-life maintenance cost exposure. If an airline expected to operate more aircraft under warranty but instead keeps older aircraft outside warranty, more technical cost shifts back to the airline.

This is what the user economics often misses: the shortage is not only “fewer new aircraft.” It is also “fewer aircraft in the protected early-life phase.” An older aircraft may require an expensive component replacement, but the operator cannot rely on new-aircraft warranty structures. The airline must pay for the part, repair, exchange unit or pooling arrangement itself.

For OEMs and parts distributors, this supports aftermarket revenue. For airlines, it increases cash pressure. For independent MROs and parts traders, it creates opportunity — especially when they can source, repair, certify and deliver parts faster than OEM channels.

Used Serviceable Material: The Value of the Aircraft That Did Not Retire

The second major impact is on used serviceable material, or USM. Under normal market conditions, aircraft retirements feed the used parts market. When an aircraft is parted out, engines, APUs, landing gear, avionics, flight controls, interiors and structural components can be removed, inspected, repaired if needed, certified and sold as serviceable material.

But when airlines delay aircraft retirements, fewer aircraft become available for teardown. This reduces the flow of used parts into the market. At the same time, demand for used parts increases because airlines need cost-effective solutions to maintain older aircraft. The result is a tighter USM market.

This is a paradox: older aircraft staying in service increase demand for used parts, but they also reduce the supply of used parts because they are not being dismantled.

For mature platforms such as the A320ceo, 737NG, 777, A330ceo and older regional jets, this can be especially significant. Airlines and MROs often prefer USM when the part is available with proper traceability and certification, because it can be cheaper and faster than buying new. However, the USM market depends on documentation quality. A part without acceptable trace, back-to-birth records where required, correct release certificates or reliable maintenance history may be commercially unattractive even if it is physically serviceable.

This makes documentation a key economic asset. In a tight spare parts market, the value difference between a properly documented component and a poorly documented one can be substantial. Airlines, lessors and parts traders increasingly need fast document review, traceability checks and compliance validation before accepting material into inventory or installing it on an aircraft.

The result is not only a parts shortage, but a documentation bottleneck.

Engine MRO: The Most Expensive Bottleneck

The strongest impact is visible in engines. Engines are the highest-value maintenance asset on most commercial aircraft. A narrowbody engine shop visit can already be expensive; a widebody engine event can become a multi-million-dollar exposure. When aircraft remain in service longer, engine utilization continues, life-limited parts consume cycles, performance deteriorates and shop visits become unavoidable.

The problem is amplified by limited engine MRO capacity. Airlines may want to send engines to the shop, but shop slots, replacement parts, LLPs, skilled labor and repair capacity are all constrained. If an engine stays longer in maintenance, the airline may need a spare engine or leased engine to keep the aircraft flying. This is why IATA identifies excess engine leasing as one of the largest cost categories linked to supply chain disruption.

New-generation engines have also created unexpected pressure. Some newer engines have faced durability issues, earlier-than-expected shop visits or inspection campaigns. That means airlines can be squeezed from both sides: older engines need more work because aircraft are staying longer, while some newer engines also require additional maintenance attention earlier than planned.

From an MRO perspective, this is a strong revenue environment. Engine shops, repair specialists, parts suppliers, DER repair providers, LLP traders and engine lessors all benefit from scarcity. However, from an airline perspective, the impact is negative unless higher ticket yields or stronger load factors offset the additional cost.

Engine economics also influence fleet decisions. An aircraft may be technically available, but if its engines require expensive shop visits, the airline must decide whether to invest in the next maintenance cycle or retire the aircraft. In a market with delayed new aircraft, the answer increasingly becomes: invest and keep flying.

Airframe and Structural MRO: The Return of Heavy Checks

Aircraft delivery delays also affect airframe maintenance. Older aircraft require scheduled checks, including heavier checks that involve deeper inspection, structural access, corrosion findings, cabin removal, system testing and repair embodiment. The exact check structure depends on the operator’s approved maintenance program and aircraft type, but the economic principle is universal: as aircraft age, heavy maintenance becomes more material.

A 25-year-old aircraft has lived through many operating environments. It may have flown in humid climates, cold climates, coastal airports, high-utilization low-cost operations or long-haul cycles. It may have accumulated multiple structural repairs, interior modifications, connectivity upgrades, avionics changes, seat reconfigurations and repaint events. Each change must be documented and maintained. Each repair may require repeat inspection. Each ageing structure requirement can add complexity.

For MRO providers, this creates demand for C-checks, structural inspections, non-destructive testing, corrosion removal, repair design, sheet metal work, composite repairs, cabin refurbishment and records review. For airlines, it creates longer downtime and higher maintenance reserves.

The aircraft can remain safe, but it becomes more expensive to operate. That distinction is essential. The issue is not that older aircraft cannot fly. The issue is that the marginal cost of keeping them in reliable commercial service rises.

Landing Gear, APUs and Components: The Secondary Wave

The impact is not limited to engines and airframes. Landing gear, APUs and rotable components are also affected.

Landing gear overhaul is driven by calendar limits and cycle limits. If aircraft retirements are delayed, some aircraft that were expected to leave the fleet before the next landing gear event may now require overhaul. That creates additional demand for landing gear shops, exchange gears, piece-part repairs and certified replacement material.

APUs see similar pressure. Older aircraft need reliable APUs for turnaround operations, air conditioning, engine start and operational flexibility. In hot climates or airports with limited ground infrastructure, APU reliability becomes operationally important. APU shop visits, exchanges and component repairs can therefore increase as older aircraft remain in service.

Rotable components — avionics, hydraulic pumps, fuel pumps, IDGs, starters, valves, actuators, oxygen equipment, wheels, brakes and many others — also experience higher demand. Airlines may increase pool stock because unpredictable lead times create operational risk. IATA explicitly identifies surplus inventory holding cost as one of the cost categories linked to current supply chain challenges.

Inventory is expensive. It ties up cash, requires storage, traceability, shelf-life control, repair management and quality oversight. But in a constrained market, not having the right part at the right time can ground an aircraft and destroy revenue. Airlines therefore accept higher inventory cost as insurance against operational disruption.

Airline Economics: Higher Cost, Less Flexibility, Stronger Pricing Pressure

For airlines, delayed aircraft deliveries create a complicated economic picture. On the revenue side, limited industry capacity can support stronger yields, especially on routes where demand is high. If competitors also lack aircraft, airlines may be able to protect fares. But on the cost side, almost everything becomes more expensive.

First, fuel cost is higher because older aircraft generally burn more fuel than new-generation aircraft. IATA’s estimate of USD 4.2 billion in delayed fuel savings shows the scale of this issue.

Second, maintenance cost rises. Older aircraft require more inspections, more component replacements, more troubleshooting and more heavy maintenance. IATA estimates USD 3.1 billion in additional maintenance costs from ageing fleets in 2025.

Third, aircraft and engine leasing costs rise. If airlines need aircraft longer, lease extensions become more expensive. If engines are stuck in shops, spare engine leases become more valuable. IATA has noted that aircraft lease rates have risen by 20–30% since 2019.

Fourth, operational flexibility declines. An airline with delayed deliveries cannot easily open new routes, increase frequencies or retire subfleets. Older aircraft may also have higher technical disruption rates, which affects schedule reliability and passenger experience.

Fifth, capital planning becomes uncertain. Airlines may have pre-delivery payments tied to future aircraft, lease commitments on existing aircraft, maintenance reserves, engine shop visit exposure and inventory investment all moving at the same time. This makes cash forecasting more difficult.

The result is a strange market: demand for air travel is strong, but the ability to convert demand into profitable growth is constrained by aircraft availability and technical cost.

The Winners: MROs, Engine Lessors, Parts Traders and Documentation Specialists

Every aviation disruption creates winners and losers. In this case, the obvious winners are MRO providers, engine lessors, spare parts distributors, USM suppliers, teardown specialists, repair shops and technical records companies.

Oliver Wyman forecasts that the global MRO market will reach USD 119 billion in 2025, surpassing the previous 2019 record by 12%, and grow to USD 156 billion by 2035. The same forecast notes that the global fleet is ageing and that older aircraft, unexpected durability issues and higher utilization are supporting MRO demand. Its 2026–2036 forecast also projects the global commercial fleet to grow from about 30,046 aircraft in 2026 to 41,135 in 2036.

This creates a favorable environment for the aftermarket. Engine shops gain pricing power. Component repair shops see stronger demand. Parts traders can monetize scarce inventory. Lessors can extend leases or place older aircraft that might previously have been difficult to remarket. Teardown companies may obtain higher value from each aircraft because serviceable parts are in demand.

Documentation and compliance service providers also benefit. In a scarce market, speed matters, but aviation cannot compromise traceability. Airlines and MROs need to know whether a part is acceptable, whether a repair is properly documented, whether life limits are clear, whether AD/SB status is known and whether back-to-birth records are complete. The more older assets remain in operation, the more important technical records become.

The Strategic Shift: Maintenance Becomes a Growth Constraint

For many years, airline strategy focused heavily on aircraft acquisition, network planning and fuel efficiency. Maintenance was sometimes treated as a cost center. That view is outdated.

In the current market, maintenance capacity is a strategic growth constraint. An airline cannot grow if it cannot secure aircraft. It cannot use aircraft if it cannot secure engines. It cannot operate engines if it cannot secure shop slots, LLPs and repairs. It cannot install components if it cannot secure certified parts and documentation. It cannot extend older aircraft if it cannot manage structural inspections and heavy checks.

Fleet planning and maintenance planning are now inseparable.

Airlines that manage this environment well will build stronger technical supply chains, diversify repair sources, improve inventory forecasting, secure engine support early, use predictive maintenance intelligently and invest in records quality. Airlines that treat the issue as temporary may face aircraft-on-ground events, expensive last-minute leases and missed revenue opportunities.

Conclusion: Delayed Deliveries Are Repricing the Whole Aircraft Lifecycle

The delays at Boeing and Airbus are not only delaying new aircraft. They are repricing the entire aircraft lifecycle.

Older aircraft are staying longer. New spare parts are harder to obtain. Used serviceable material is becoming more valuable. Engine MRO capacity is under pressure. Structural checks are more important. Landing gear, APUs and components are seeing higher demand. Airlines are carrying more inventory, paying more for maintenance and losing part of the fuel savings they expected from fleet renewal.

For aircraft owners, lessors, MROs and parts suppliers, this is a period of opportunity. Assets that looked close to retirement may now produce several more years of revenue. Inventories that seemed slow-moving may become valuable. Repair capability may be worth more than new production exposure. Technical documentation may become a commercial differentiator.

For airlines, however, the situation is more difficult. Strong passenger demand is helpful, but aircraft scarcity increases cost and reduces flexibility. The economic advantage goes to airlines that can keep aircraft reliable, secure maintenance capacity and manage technical risk better than competitors.

The central lesson is simple: when new aircraft do not arrive, the old aircraft does not disappear. It becomes more valuable, more expensive, more maintenance-intensive and more strategically important.

The aftermarket is no longer just supporting the fleet. In today’s supply-constrained aviation market, the aftermarket is keeping the industry flying.

© 2026 Millhouse Consulting Kulinský / Alexandr Kulinsky. All rights reserved.

This is an original Millhouse.ch publication. Reproduction, republication, distribution or commercial use requires prior written permission, except where permitted by law. This publication may be declared to ProLitteris for copyright remuneration purposes.