21 Jan 2026

Spare Engines as Strategy: The Asset Class Inside the Asset Class

A spare engine has traditionally been treated as a technical contingency, something operations teams worried about when an aircraft went AOG and engineers needed a quick swap. In 2026, that mindset no longer holds. Engine availability now sits at the centre of operational resilience, and the difference between flying and waiting is often determined not by fleet size, but by access to spare powerplants.

What has changed is the environment around engines. Extended shop visit timelines, constrained MRO capacity, and uneven post-pandemic recovery have turned spare engines into scarce, high-value assets. For airlines and lessors alike, spare engines now behave like a distinct asset class with their own capital requirements, utilisation risks, and strategic importance, demanding the same level of planning as fleet capacity itself.

 

What is a spare engine strategy in commercial aviation?

A spare engine strategy is the planned approach airlines and lessors use to ensure continuous aircraft operations when engines are removed for maintenance, inspection, or unexpected events. Instead of reacting to AOG situations as they arise, this strategy defines how spare engines are owned, leased, pooled, or accessed so that aircraft can return to service quickly and predictably.

Its importance becomes clear when you look at what it protects across the operation:

• Keeps aircraft flying during scheduled and unscheduled engine removals
• Reduces costly AOG time and schedule disruption
• Limits revenue loss during extended shop visits
• Improves operational reliability during periods of engine scarcity
• Provides flexibility when maintenance timelines slip
• Protects fleet utilisation during peak demand periods

In today’s constrained engine market, a spare engine strategy is less about having a backup and more about managing exposure. It ensures engine availability is planned, priced, and aligned with fleet operations rather than left to chance.

 

Why have spare engines become critical in 2026?

In 2026, spare engines have moved from being a contingency buffer to a core operational requirement. Airlines are facing longer engine shop visit times, tighter MRO capacity, and unpredictable removals, all while fleet utilisation has returned faster than the supply chain can support. In this environment, engine access directly determines whether an aircraft generates revenue or sits idle.

The reasons behind this shift are structural and interconnected:

• Extended shop visit durations: Engine inductions are taking months longer than planned, increasing the need for off-wing coverage.
• MRO capacity constraints: Limited shop slots mean even well-planned maintenance can face delays.
• Post-pandemic utilisation spikes: Aircraft are flying harder, accelerating engine removals and LLP consumption.
• Parts and material shortages: Delays in modules and components slow repairs and return-to-service timelines.
• Higher AOG cost exposure: Each grounded aircraft now carries a greater revenue and reputational penalty.

As a result, spare engines are no longer just operational insurance. They are a strategic asset that determines resilience, schedule stability, and the ability to operate reliably in a capacity-constrained market.

 

How do spare engines reduce AOG risk for airlines?

Spare engines reduce AOG risk by removing dependency on uncertain repair timelines. When an on-wing engine must be removed unexpectedly or inducted earlier than planned, immediate access to a serviceable spare allows the aircraft to return to service without waiting for shop completion. This shifts AOG risk from an open-ended disruption to a controlled, time-bound event.

The process works by separating aircraft availability from engine availability:

• An unserviceable engine is removed and sent for maintenance or overhaul
• A spare engine is installed to restore the aircraft to service
• The aircraft resumes operations while the removed engine progresses through the shop
• Operational schedules remain intact despite maintenance delays

This mechanism also stabilises decision-making across the operation:

• Maintenance planning becomes less reactive
• Schedule recovery is faster after unscheduled removals
• Exposure to cascading delays across the network is reduced
• Revenue loss from prolonged grounding is avoided

In effect, spare engines convert uncertainty into planning. Instead of waiting on engine shops, airlines maintain control over fleet availability, making AOG events manageable rather than disruptive.

 

What types of aircraft and engines require spare coverage?

The need for spare engine coverage depends on aircraft size, utilisation intensity, and maintenance complexity. Aircraft operating long hours, flying dense schedules, or relying on limited engine types face higher exposure when an engine is removed from service. In these cases, spare coverage becomes essential to protect fleet availability.

Spare engine strategies are most critical for:

• Narrowbody aircraft operating high-frequency, short-cycle routes
• Widebody aircraft on long-haul services with limited schedule flexibility
• Aircraft powered by engines with known shop capacity constraints
• Fleets with high commonality where multiple aircraft depend on the same engine type
• Aircraft operating in regions with limited local MRO access

Without spare coverage, these aircraft are far more vulnerable to extended AOG events. As utilisation rises and maintenance timelines stretch, spare engines provide the buffer that keeps fleets moving and schedules intact.

 

How do airlines access spare engines without owning them?

Airlines increasingly rely on access-based models to secure spare engines without tying up large amounts of capital. These structures are designed to prioritise availability, response time, and flexibility rather than ownership.

Common access methods include:

• Short- and long-term engine leasing to cover planned or unexpected removals
• Participation in engine pooling programmes shared across multiple operators
• Power-by-the-hour agreements with guaranteed spare engine support
• Access contracts linked to AOG response times rather than asset ownership
• Strategic arrangements with MRO providers for standby engine availability

By using these models, airlines can maintain operational resilience while keeping spare engine exposure aligned with fleet size, utilisation, and financial capacity.

 

What role do engine leasing and pooling models play?

Engine leasing and pooling models sit at the heart of modern spare engine strategies. They allow airlines to secure access to engines when needed, without carrying the full capital and utilisation risk of ownership. In a constrained engine market, these models have shifted from being supplementary options to primary tools for managing operational resilience.

Their role becomes clearer when you look at how each model is used in practice:

• Engine leasing provides dedicated access to a specific spare engine for a defined period
• Pooling spreads availability across multiple operators, improving flexibility
• Leasing suits predictable, long-duration coverage needs
• Pooling works best for short-term, unpredictable AOG events

Both reduce upfront capital requirements compared to ownership

 

 

Ultimately, leasing and pooling are not interchangeable. They are complementary tools. Used correctly, they allow airlines to match spare engine access to utilisation patterns, risk tolerance, and financial constraints, ensuring coverage is available when it matters most without overcommitting capital.

 

How do PBH agreements change spare engine economics?

Power-by-the-hour (PBH) agreements change spare engine economics by shifting cost from ownership and capital expenditure to predictable, usage-based payments. Instead of holding spare engines or arranging ad hoc access, airlines pay a fixed rate per flight hour that typically includes maintenance coverage and guaranteed spare engine support. This transforms spare engines from balance sheet assets into operating expenses.

PBH agreements reshape economics in several key ways:

• Reduce upfront capital tied to spare engine ownership
• Convert variable AOG risk into predictable hourly costs
• Transfer availability and maintenance risk to the provider
• Improve cashflow visibility and budgeting accuracy
• Scale spare coverage with actual aircraft utilisation
• Lower exposure during periods of uncertain demand

By linking engine access directly to utilisation, PBH agreements align cost with revenue generation, making spare engine planning more flexible and financially resilient in volatile operating environments.

 

Why is spare engine forecasting so difficult?

Spare engine forecasting is challenging because it sits at the intersection of maintenance uncertainty, operational variability, and capital constraints. Engine removals rarely follow clean, linear schedules, and small changes in utilisation or shop performance can quickly cascade into availability gaps.

The difficulty comes from several overlapping factors:

• Unplanned engine removals driven by reliability issues or findings on wing
• Highly variable shop visit durations influenced by parts, labour, and findings
• Limited visibility on MRO slot availability and turnaround times
• Changes in utilisation that accelerate or delay engine life consumption
• Pool availability that fluctuates during industry-wide disruption
• Capital constraints that limit how many spares can be economically held

Because of these variables, spare engine planning is never static. Forecasts must be continuously updated, stress-tested, and aligned with real operational data. Without this discipline, airlines either over-invest in underutilised assets or discover gaps only when aircraft are already grounded.

 

What risks do lessors face with spare engine allocation?

Lessors face increasing risk around spare engine allocation because engine availability directly affects aircraft uptime, lease performance, and asset value. When spare engines are scarce, disputes can arise over priority access, especially within pooled or shared arrangements. Lessors also carry indirect exposure if an operator’s lack of engine access leads to prolonged AOG events, reduced lease payments, or strained redelivery conditions. As engine scarcity persists, lessors must assess not just who operates the aircraft, but whether that operator has credible, contractually secured access to spare engines throughout the lease term.

 

How should spare engines be treated in fleet and asset planning?

Spare engines can no longer be treated as technical contingencies or ad hoc solutions. In a constrained maintenance environment, engine access has become a core determinant of fleet availability, revenue stability, and asset performance. Planning for spare engines now requires the same discipline as planning aircraft capacity, financing, and deployment.

For airlines and lessors alike, the question is no longer whether spare engines are needed, but how deliberately that exposure is managed. Ownership, leasing, pooling, and PBH structures each play a role, but only when aligned to utilisation, risk tolerance, and capital strategy. Do you have clear visibility on where your engine risk sits across the portfolio, or are you discovering it only when aircraft stop flying?

 

FAQs

 

Q: Do all airlines need to own spare engines?

A: No. Many airlines rely on leasing, pooling, or PBH agreements instead of ownership.

Q: Are spare engines only relevant during AOG events?

A: No. They also support planned maintenance and protect schedule reliability.

Q: Do spare engines affect aircraft lease value?

A: Yes. Poor engine access can reduce utilisation and impact asset performance.

Q: Can pooling fully replace spare engine ownership?

A: Not always. Pooling works best alongside other access models.

Q: Why is spare engine planning more complex today?

A: Longer shop times and limited capacity make availability harder to predict.