AOG stands for Aircraft on Ground. In aviation maintenance and operations, it describes a situation in which an aircraft cannot continue its planned operation because a technical issue, maintenance requirement or other condition prevents it from being released for service.
An AOG event can create significant operational disruption because the aircraft is unavailable while Engineering and Maintenance determine the cause, obtain the required parts or technical support, complete the necessary work and return the aircraft to service.
What can cause an AOG?
AOG events can result from many different technical situations. Examples include aircraft defects, component failures, maintenance findings, unavailable spare parts or conditions that require additional engineering assessment before the aircraft can be released.
The operational impact depends on factors such as where the aircraft is located, the availability of replacement parts and maintenance support, whether troubleshooting is required and whether another aircraft can cover the planned operation.
For this reason, AOG management often involves coordination between Maintenance Control, Engineering, Reliability, Supply Chain and Operations.
AOG and Aircraft Reliability
Individual AOG events are important operationally, but their wider value for Reliability Engineering comes from understanding the patterns behind them.
Repeated defects, unscheduled component removals, technical delays and recurring problems within particular ATA chapters can provide useful indications of where fleet reliability is deteriorating.
Reliability teams therefore analyse AOG-related events together with defects, component history, aircraft utilisation and maintenance data to understand which aircraft, systems or components require closer attention.
Read more about how EXSYN supports this broader process through Reliability Intelligence.
From AOG Events to Earlier Risk Detection
Historical maintenance and reliability information can also be used to identify patterns associated with previous AOG events.
Instead of reviewing each grounding only after it occurs, Engineering teams can monitor recurring defects, component removals and other reliability indicators to determine where emerging risk may deserve investigation.
EXSYN’s AOG Risk Monitor is designed to support this earlier-risk view by bringing relevant defect, component and maintenance information together for Engineering review.
The objective is to give engineers greater visibility into developing risk while leaving maintenance and operational decisions with the airline.
AOG and Technical Dispatch Reliability
AOG events can also affect technical dispatch reliability, particularly when technical problems lead to delays, cancellations or aircraft changes.
For Reliability Engineers, the overall dispatch-reliability percentage is only the starting point. Understanding which defects, aircraft or systems are driving the disruption provides the context required for further investigation.
See our guide to Technical Dispatch Reliability and technical delays for a deeper explanation.
