AOG (Aircraft on Ground): what it is, causes, impacts, and logistics management

When an aircraft is grounded due to a technical or operational issue, it’s not just an unexpected maintenance event: it becomes a true “crisis mode” for aviation and the supply chain. In an AOG scenario, time becomes the most critical variable—every hour of downtime affects the network, costs, and service continuity, triggering a chain of urgent decisions involving airlines, MROs, suppliers, handlers, and logistics partners.

In this article by Savino Del Bene, we’ll explain what an AOG is, the most common causes, the consequences it can generate, and how an AOG shipment can be managed operationally in a structured and reliable way.

What is an AOG (Aircraft on Ground) and when does it become an emergency?

AOG stands for Aircraft on Ground and refers to a situation in which an airplane/aircraft cannot fly and is therefore grounded due to technical issues, failures, or the need for maintenance interventions.

In practice, the meaning of AOG is not limited to the aircraft’s status: “AOG” often becomes an operational label used to identify spare parts, materials, and shipments that must arrive as quickly as possible to return the aircraft to service.

An emergency arises when the downtime cannot be handled through standard solutions (local stock, maintenance planning, simple re-accommodation) and a rapid response is required: immediate sourcing of the component, selection of the fastest transport option, and tight coordination all the way through delivery.

AOG impacts: what are the consequences?

An AOG affects multiple levels: it is not limited to the cost of the repair, but creates a cascading effect across operations and planning. The most common consequences include:

• Aircraft downtime: a grounded aircraft does not generate revenue and disrupts the planned rotation. Depending on the route and type of service, downtime can lead to cancellations or reduced available capacity, with immediate impacts on the network and on-time performance KPIs;
• Rescheduling crews and assets: crew shifts and assignments change, slots and operational priorities are revised, and in some cases an aircraft substitution is evaluated. This can create a domino effect across multiple flights in the same rotation chain;
• Cargo re-accommodation: cargo may be rebooked on other flights or rerouted through alternative gateways, with potential delays, changes in handling, and the need to update documents and milestones. For certain types of cargo, the risk of additional costs and non-compliance also increases;
• Extraordinary costs and 24/7 operations: to reduce ground time, urgent and non-standard solutions may be activated (priority uplift, time-critical couriers, dedicated charters, controlled last mile), along with continuous operational coverage to coordinate all parties involved;
• Impact on service and customer experience: when the aircraft is part of a complex network, an AOG can affect SLAs and perceived reliability, requiring timely communication with customers and partners to manage expectations and alternatives.

What are the most common causes of an AOG?

The causes of an AOG can vary, but in most cases they fall into a few macro-categories that directly influence the timing and approach of the logistics response:

• Technical failures and unexpected malfunctions: issues affecting components or systems (avionics, hydraulics, pneumatics, electrical systems, landing gear, etc.) that make the aircraft unfit to fly until restored. In these cases, urgency is often driven by how quickly the critical part is identified and sourcing is activated;
• Unplanned maintenance and findings during inspections: anomalies detected during inspections or following operational reports that require immediate intervention. Even when a failure is not “catastrophic,” it can still ground the aircraft if the intervention cannot be postponed or if the necessary material is not available;
• Unavailability of critical spares (stock-out or distance from the point of intervention): the component is not available locally and must be sourced from another airport, warehouse, or supplier. This is one of the most frequent drivers of AOG shipments because it turns a technical issue into a time-to-deliver issue;
• Documentation errors or information misalignment: incomplete or incorrect data on part number/serial number, documentation not ready, misaligned instructions, or missing authorizations can slow down the shipment, customs clearance, or delivery to airside/landside. In an emergency, even a small inconsistency can translate into hours lost;
• Operational and logistics constraints: tight cut-offs, flight cancellations, handling limits, or restrictions on certain materials can complicate the solution and require alternative routings, special modes, or backup plans that are already prepared.

How is an AOG managed?

Managing an AOG (Aircraft on Ground) requires a highly operational approach, because the goal is not simply to “ship a spare part,” but to reduce aircraft downtime by quickly coordinating all the activities needed to return it to service. For this reason, the first step is to collect and validate essential information (requested part and references, shipment characteristics, delivery point, time window, and contacts): in a time-critical context, even incomplete data can generate delays.

Once the request is defined, the process moves to sourcing the component, verifying where it is available (warehouses, pools, suppliers, OEMs) and selecting the most reliable solution based on the deadline. In parallel, the best transport option is built, taking into account cut-offs, flight availability, handling constraints, and the last mile. The difference versus a standard shipment is that routing is set with a higher level of control and, when needed, with ready-to-activate alternatives (for example, different gateways or dedicated modes) to avoid losing time in case of unexpected events.

Another critical node is document management and, where applicable, customs handling: urgency is not only about transit time, but also about being able to release and deliver the spare part without holds. Finally, execution requires proactive monitoring and continuous communication through delivery at the correct operational point, with immediate confirmation of successful delivery.

In operations like these, the difference is often made by the ability to ensure coverage, responsiveness, and international coordination. If you are interested in the topic, you can learn more about Savino Del Bene’s approach through its services for the aerospace sector.

AOG logistics: what makes an aerospace shipment “time-critical”?

An AOG shipment is not simply a “faster shipment.” It is a shipment in which the entire process is designed to reduce the risk of time loss (delays) and manage exceptions proactively. The elements that make “grounded aircraft” logistics time-critical include:

• Tight cut-offs and narrow operating windows (for flights, handling, airside/landside deliveries);
• Absolute priority and rapid decision-making (route, gateway, ready alternative solution);
• Backup plans: alternatives already defined if a flight is missed or operating conditions change;
• Proactive tracking: it is not enough to “see” status—risks must be anticipated and actions taken before they become delays.

Below is a summary table of the differences between standard shipments and AOG shipments.

How to reduce AOG risk

Reducing AOG risk does not mean eliminating it, but decreasing its frequency and impact through a mix of technical prevention and logistics preparedness. The first lever is operational readiness: defining a clear AOG protocol (roles, contacts, escalation paths, minimum data to collect), activatable 24/7 and replicable across all locations/critical areas.

The second lever is the spare parts strategy. Beyond in-house stock, what matters is positioning: stock—or access to pools/rotables—near the most sensitive hubs, replenishment criteria based on criticality and lead time, and supplier agreements to reduce sourcing time. Even strong management of “smaller” fast-moving parts can prevent a minor issue from turning into aircraft downtime.

A third element is data quality and visibility. Many AOG slowdowns stem from misalignment on part number/serial, instructions, documentation, and milestones. Integrating and standardizing information flows (ERP/TMS/WMS and partner systems), with proactive tracking and exception alerts, helps prevent errors and react before an unexpected event turns into a delay.

Finally, the more “long-term” lever is predictive maintenance, which allows anomalies to be detected before an aircraft is grounded and helps plan interventions and spare availability, reducing unplanned AOG events. The best outcome is achieved when maintenance, stock, and logistics work as a single system: fewer “true” emergencies and, when they occur, a faster and more controlled response.

Conclusion

Are you managing an AOG shipment or looking to set up a protocol to reduce time and risk when an aircraft is grounded at Fiumicino? The difference between an effective response and prolonged downtime is often a structured approach: accurate information from the start, a clear workflow, backup plans, and operational visibility through delivery.

In Italy, Savino Del Bene provides a dedicated Aircraft On Ground service (operating exclusively at Fiumicino), with a service desk available 15 hours a day, 365 days a year, designed to ensure close monitoring and on-time delivery of the required spare parts. Contact your local representative today for a dedicated consultation.