Engine MRO Unpredictability Drives Spares Market Squeeze

Uncertain engine removals, shop turnaround times and repair costs are creating a new layer of aftermarket complexity, forcing airlines and MROs to build greater flexibility into maintenance planning.

As new-generation engines enter service, the challenge for airlines and MRO providers is simply not knowing when an engine will require maintenance. Increasingly, the conundrum extends beyond predicting when an engine will come off wing to forecast the scope, duration and cost of the shop visit that follows.

PREDICTABILITY PROGRESS

“Generally speaking, engine maintenance predictability is actually getting better with the ascendance and implementation of new technologies that collect and make sense of engine performance data,” says Marcel Leon de Paz, vice president of programs and sales at MTU Maintenance Berlin-Brandenburg.

The perception of reduced predictability is driven by the wider operating environment, he says, including supply chain constraints, rapid fleet growth, new engine introductions and external disruptions. The transition to new engine generations is also happening faster and across a larger market than in previous cycles.

BeauTech Power Systems sees uncertainty continuing well beyond the initial removal. Chief Operating Officer Tobias Konrad says shop turnaround times (TAT) and repair costs can be just as difficult to predict as the removals themselves.

“You can source a spare to bridge a gap, but you cannot plan around a shop visit whose duration and price you can’t forecast,” he contends, adding that is what determines how long the spare is actually needed and how much the whole exercise costs. “Right now, neither is predictable,” he says. “The engine on the ground is the symptom everyone sees. The TAT and the cost of the repair are the part that really hurts.”

Likewise, Pratt & Whitney sees predictability becoming a more important consideration in engine development. Keren Rambow, vice president of geared turbofan (GTF) aftermarket and transformation, says durability and maintenance predictability have become priorities alongside fuel efficiency. The company is working with airlines to improve the ability to anticipate removals and preposition material and repair capability for each individual engine, enabled by connectivity across systems.

For MTU, predictability ultimately extends beyond the removal itself. “It is also about accurately forecasting the scope, cost and TAT of the shop visit,” Leon de Paz says. From MTU’s perspective, one of the most important enablers is boosting repair capability across the aftermarket. Besides technical development, this requires broader access to repair technologies, licensing frameworks and closer industry collaboration.

CAPACITY CONSTRAINTS

For MRO providers, the challenge posed by less predictable engine removals is in absorbing additional work without disrupting the scheduled maintenance already in the shop. The problem is particularly acute when unexpected inductions arrive against a backdrop of high overall shop-visit demand and extended induction times.

StandardAero says newly introduced engine types can experience early service issues that lead to earlier-than-expected shop visits, requiring MROs to remain flexible in how they allocate capacity and the types of work they accept. Olivier Ruffet, vice president of sales for Europe, the Middle East and Africa and lessors, says the current level of demand and longer induction times are the biggest challenges when balancing scheduled maintenance with unexpected inductions.

StandardAero also is adapting its service model to give operators alternatives when a full shop visit cannot be accommodated immediately. Its response includes short-term engine leases, exchange engines, module swaps and flexible induction options. On-wing support can also be used to minimize aircraft-on-ground events where appropriate.

MTU Maintenance takes a similar approach, planning for multiple capacity scenarios so it can accommodate scheduled demand alongside a defined level of ad hoc requirements. Leon de Paz says cross-qualified personnel, adaptable shop capacity, material planning and flexible resource allocation allow the company to respond as requirements change.

“Unscheduled events tend to involve lighter work scopes and rarely justify a full shop visit, but they happen often enough that providers need to build them into their operational planning and resource allocation,” Leon de Paz adds.

For instance, at MTU’s Berlin-Brandenburg facility, a dedicated “hospital shop” operates alongside the main overhaul facility, handling smaller and one-off work scopes separately. The arrangement is intended to provide additional flexibility while protecting the schedule for planned maintenance.

KNOCK-ON EFFECTS

Uncertainty around shop visits is also putting pressure on the spare-engine market. The longer an engine remains in the shop, the longer an airline needs a replacement, increasing both costs and exposure to spare engine availability.

Konrad says the market for new-generation engine spares has effectively split between airlines covered by comprehensive OEM maintenance programs and those exposed to the third-party market. For operators with OEM coverage, the programs typically specify a spare-engine ratio, with the OEM expected to provide additional spares where an airline’s own holdings fall short.

However, the recent accumulation of issues affecting the GTF and CFM International Leap exposed a gap between contractual coverage and physical availability.

“Even where the OEM was contractually on the hook to provide a spare against a removal, there were no spares left to give,” Konrad says. The result was aircraft being parked despite the existence of contractual spare coverage.

Airlines without OEM coverage faced an even tighter market, with their own engines sitting in long induction queues as they searched for replacements. That drove demand for lease engines and pushed rates higher, Konrad says. He emphasizes that airlines do not hesitate to pay the premium—when the choice is between keeping an aircraft on the ground or snapping up whatever green‑time engine is available, they reach for the checkbook.

Konrad says airlines are more inclined to hold additional spare engines when availability is tight and prices are rising, further increasing demand across the market. “As engines get scarce and expensive, airlines get nervous, and nervous airlines select more spares than they’d actually like to carry, just to be safe,” he says. That kind of overselection only tightens the market further, driving prices up yet again. He sees it as a self‑-reinforcing cycle, one that is still feeding on itself.

REPAIRS AND UPGRADES

Even when an engine reaches an MRO facility, the availability of approved repair solutions can determine how much of the engine can be restored, how much material must be replaced and ultimately how long the shop visit takes.

Konrad holds this remains a significant issue for the GTF and Leap. While additional MRO capacity should help ease shop-slot constraints, he says the more difficult question is when piece-part repair capability will improve. “At this stage, a lot of parts simply have to be scrapped, not because anyone wants to, but because the approved repairs don’t exist yet,” he says. Konrad also notes that tearing down a used Leap or GTF currently makes very little financial sense. “If you can’t repair the parts and have to scrap them, you don’t have the harvestable green-time material that makes a teardown pay,” he says.

StandardAero expects maintenance predictability to improve as early service issues are addressed and time on wing improves. “That said, the fact that airlines and asset owners have by now become used to the wide variety of support offerings introduced by MROs in recent years probably means that service flexibility is here to stay,” Ruffet predicts.

Meanwhile, MTU is maintaining a deliberate push on repair development and shop capacity, working closely with OEM partners to bring more certified solutions into the engine maintenance mix. As the pool of proven repairs expands, operators become less reliant on new material and the supply chain chokepoints that continue to shape the aftermarket.

For Pratt & Whitney, reducing the cost and disruption associated with maintenance unpredictability starts with improving engine durability and making maintenance requirements more predictable. Rambow says the company is incorporating new hot-section parts into production engines and during MRO visits to increase GTF time on wing.

The new GTF Advantage engine is also designed to deliver up to double the time on wing of today’s GTF engine, while the in-development GTF Hot Section Plus upgrade is intended to provide current PW1100G-JM operators with up to 90-95% of the durability benefits of the GTF Advantage. The PW1100G-JM engine production line is expected to transition fully to the GTF Advantage specification in 2028, Rambow says.

Pratt & Whitney is also using engine data to improve the predictability of maintenance requirements. Rambow says the company is working with airline customers to automate engine data delivery, enabling real-time understanding of how individual engines are operating and better material and repair signals for the MRO network.

The value of that data extends beyond health monitoring, she says. It can provide a feedback loop for supply chain demand, repair strategy and shop flow, while a life-cycle digital thread can connect information from engine design and manufacturing through in-service operation and maintenance.

For operators, the aim is to ultimately reduce the uncertainty that drives additional maintenance costs and operational disruption. As Pratt & Whitney continues to develop its digital capabilities, Rambow says predictive maintenance models will move toward “prescriptive and autonomous maintenance.”