AOG Support and Aircraft Spares Provisioning: Pooling, Consignment, and Power-by-the-Hour

"Aircraft MRO providers for A380 heavy maintenance in the Gulf" and "MRO providers in Dubai" are visible queries, but behind them sits a quieter, continuous procurement problem every operator faces: how to have the right part in the right place when an aircraft is grounded — or, better, before it is. An AOG (Aircraft On Ground) event, where a missing or failed part stops a revenue aircraft from flying, is one of the most expensive situations in aviation. This brief explains AOG support and the main spares-provisioning models — pooling, consignment, exchange, and power-by-the-hour — that GCC airlines and MROs use to manage parts availability and cost.

What AOG means and why it is so costly

AOG is the term for an aircraft that cannot fly because it needs a part or repair that is not immediately available. A grounded widebody represents lost revenue, disrupted schedules, displaced passengers and knock-on network effects — the cost of a single AOG day can dwarf the cost of the part itself. AOG desks (run by airlines, MROs and parts suppliers) operate around the clock to locate, expedite and ship the needed part, often by the fastest available freight, to get the aircraft back in service. The whole discipline of spares provisioning exists to minimise both the frequency and the duration of AOG events.

The provisioning models

Operators rarely buy and warehouse every part outright — that ties up enormous capital in inventory that mostly sits unused. Instead they use a mix of models:

• Outright purchase — the operator buys and owns the spare. Simple, but capital-intensive and exposes the operator to obsolescence and the cost of holding rotables (repairable units) that depreciate.
• Pooling — multiple operators (or an operator and a pool provider) share access to a common inventory of spares, drawing parts as needed and returning unserviceable units for repair. Pooling spreads the cost and improves availability without each operator holding a full set. It is especially valuable for expensive rotables that are needed rarely but urgently.
• Consignment stock — a supplier places its own inventory at the operator's or MRO's location; the operator draws from it and pays only when a part is used. The supplier owns the stock until consumed, reducing the operator's working-capital tie-up while keeping parts on hand.
• Exchange / loan — the operator receives a serviceable unit and returns the removed (unserviceable) unit for repair, paying an exchange fee plus the repair cost. Avoids buying a spare outright while keeping turnaround fast.
• Power-by-the-Hour (PBH) / flight-hour agreements — the operator pays a rate per flight hour (or per cycle) and the provider guarantees component availability, repair and often pooling access. PBH converts a variable, lumpy maintenance-spares cost into a predictable per-hour cost and shifts inventory risk to the provider. It is widely used for components and increasingly for engines and APUs (engine programmes such as the OEMs' flight-hour services being the largest examples).

Most large operators run a blend: PBH or pooling for expensive rotables, consignment for high-use consumables, and outright purchase for cheap or operator-specific items.

Why traceability and certification gate every spare

A spare is only usable if its airworthiness is documented. Every part fitted to a certified aircraft must come with the correct release certification — an EASA Form 1 or FAA 8130-3 authorised release certificate — establishing that it was manufactured or maintained by an approved organisation and is airworthy. (See the dedicated briefs on EASA/FAA certification forms and on EASA Part-145 vs FAA Repair Stations.) This is why parts cannot simply be sourced on price: an uncertified or improperly documented part — or a Suspected Unapproved Part (SUP) — cannot legally be fitted, regardless of cost or urgency. AOG pressure is exactly when documentation discipline matters most, because the temptation to cut corners is highest.

The standards and bodies

• EASA Part-145 / FAA Part 145 — the maintenance-organisation approvals under which repairs are done and parts released.
• EASA Form 1 / FAA 8130-3 — the authorised release certificates that accompany serviceable parts.
• ASA-100 / FAA AC 00-56 — accreditation for civil aircraft parts distributors, giving buyers confidence in a distributor's quality system and traceability.
• ATA Spec 2000 — the industry data standards for spares ordering, procurement and provisioning messaging, used in pooling and supply-chain systems.
• IATA guidance on materials management and the broader supply chain.

GCC-specific considerations

• Major Gulf carriers and engineering arms (Emirates Engineering, Etihad Engineering, Saudia/SAEI, Qatar Airways Technical, Oman Air Engineering) run large spares operations and often provide third-party MRO and parts services to others in the region.
• Geography is an advantage — the Gulf's central position and major freight hubs (Dubai, Doha) make it well placed for AOG logistics and regional pooling, but customs clearance speed for AOG shipments is a real operational factor.
• A380 and very-large-aircraft spares are specialised and concentrated; provisioning for rare, high-value rotables suits pooling/PBH models.
• Local-content and agent rules (see the GCC procurement brief) can affect how foreign parts suppliers and distributors operate in-region.
• Customs and import handling for AOG-critical shipments — expedited clearance arrangements materially affect AOG downtime.

What this means for procurement

Spares provisioning is a portfolio decision, not a single buy. Map the fleet's components by value, criticality and usage rate, then match each band to the right model: PBH or pooling for expensive, rarely-needed rotables where availability is everything; consignment for high-turnover consumables; exchange for fast component swaps; outright purchase only where it genuinely pays. Underpin all of it with non-negotiable traceability — EASA Form 1 / FAA 8130-3 on every serviceable part, accredited distributors (ASA-100), and disciplined documentation even under AOG pressure. Providers in this space include the airframe and engine OEMs' aftermarket arms, independent distributors and pool operators (AJW, Satair, Lufthansa Technik, AAR, and others), and the Gulf engineering arms themselves. The cheapest part with the wrong paperwork is the most expensive mistake in the chain.