AOG Delays: When Rotables and Missing Assets Ground Your Aircraft

In the Aerospace & Defense (A&D) industry, every second counts. Maintenance, Repair, and Overhaul (MRO) operations must function like clockwork, with zero tolerance for delays. Yet one of the most costly and persistent disruptions to these processes stems from something deceptively simple: not knowing where essential tools and components—like torque wrenches, borescopes, engine cowlings, landing gear actuators, tool carts and maintenance trolleys, spare parts bins or storage containers—are.

Aircraft on Ground (AOG) events—when an aircraft is grounded due to maintenance issues—can result in millions in losses and penalties due to contractual obligations with airlines. But what if the delay is due not to a complex mechanical failure and its repairing process, but a single, misplaced part—particularly a rotable?

What Is AOG (Aircraft on Ground)?

AOG refers to situations where an aircraft is grounded due to a maintenance issue that must be resolved before it can return to service. These events create an immediate need for repair or replacement of specific components. AOG incidents not only disrupt flight schedules but also delay military readiness, impacting high-stakes defense missions and costing airlines and contractors tens or even hundreds of thousands of dollars per hour. And when the cause is a missing or unavailable rotable part, the financial and operational impact escalates quickly.

A Silent Profit Killer: Why a Few Rotables and Missing Tools Drive Most AOG Costs

Rotables are high-value aircraft components—such as avionics systems, brakes, or actuators—that can be repeatedly repaired, overhauled, and returned to service. These parts are essential for safe operations and are managed under tightly regulated maintenance schedules. But when they go missing or are delayed, the consequences can be severe.

A detailed study on the Boeing 777 fleet at one airline revealed just how critical these parts are: 25 rotables out of 115 parts—just 21.74%—accounted for an astounding 91.04% of AOG-related costs.

Rotables are not the only culprits. A misplaced specialty tool—such as a rivet gun, engine brackets, or a calibrated torque wrench—can paralyze an entire repair operation. And the issue is not confined to a single MRO shop. Across the globe, support equipment like engine mountings and tooling frequently go missing or arrive late due to fragmented visibility.

Despite millions in infrastructure investments, many MROs still rely on paper-based systems, siloed spreadsheets, or tribal knowledge to locate grounding-risk parts.

The result?

Average replenishment cost per AOG event: $8,785

Average flight delay cost per AOG event: $22,754

Total per incident: over $31,500

That is before factoring in the ripple effect across schedules, productivity, and readiness. To put this into perspective, Boeing estimates that a single AOG event can cost anywhere from $10,000 to $150,000 per hour, depending on aircraft type and route. Every untracked hour amplifies the operational and financial damage.

The underlying causes are frustratingly familiar to MRO teams:

Delays due to misplaced or misallocated inventory

Misuse or expiry of certified parts

Maintenance backlogs when critical rotables are unavailable

Cost spikes from urgent procurement or expedited production

An ABC analysis of rotable usage and delay frequency confirms what crews already know: a few components and tools cause most of the pain. And it's not just about cost—it’s about visibility.

These parts and tools often disappear into uncoordinated logistics chains, bounce between locations, or fall off the radar altogether due to inadequate tracking. Whether it’s a torque wrench missing in a local hangar or a set of engine brackets in transit between continents, the outcome is the same: downtime and disruption.

In an industry where minutes matter and operations are globally connected, real-time visibility into critical assets is no longer optional. It demands a system-agnostic approach to asset tracking—one that bridges data, location, and process across tools, rotables, and fleets, wherever they are.

How Real-Time Asset Tracking Prevents Costly AOG Events

Real-Time Location Systems (RTLS) close these visibility and traceability gaps. By combining technologies like Ultra-Wideband (UWB), RFID, GPS, and BLE, aerospace organizations gain precise, instant insights into where their tools, rotables, and assets are—at all times and highly accurate.

With KINEXON Platform, A&D maintenance and logistics teams can integrate various location technologies and benefit from:

Labour efficiency through workflow automation

Receive automated alerts when parts or tools go missing

Track work-in-progress (WIP) through every maintenance stage

Better quality control and on-time delivery performance

Locate rotables with 10 cm accuracy in crowded warehouses or hangars

Ensure regulatory compliance with automated documentation trails

Predict maintenance needs through digital twins and performance analytics

From Reactive to Proactive: Transforming AOG Management

It is not just about real-time tracking—it is about intelligent, automated, and connected operations. When MRO organizations centralize their asset data, integrate it with existing ERP/MES/WMS systems, and automate workflows, they reduce turnaround time (TAT), minimize disruptions, and maximize mission readiness.

And for rotables in particular, this means:

No more lost inventory: Real-time tracking and automated bookings ensure that every part, tool, or component is always accounted for

No more duplicate rush orders: Avoid costly and unnecessary reorders triggered by misplaced tools or parts that are mistakenly assumed lost.

No more maintenance halts and contractual penalties due to unknown location or condition: Real-time tracking ensures quick access to tools and parts, preventing delays from misplaced or unaccounted assets

Final Thoughts: Visibility = Readiness

In Aerospace & Defense and MRO, the cost of not knowing is immense. Whether it is a rotable or a specialized tool, the inability to instantly locate high-impact assets leads to delays that ripple across flight schedules, defense readiness, and budgets. The solution is clear: embrace real-time asset tracking. With platforms like KINEXON, the most critical assets—especially rotables—are always visible, traceable, and available when needed. In an industry where the difference between “grounded” and “go” can come down to a single missing component, operating without full visibility is simply not an option.

Benefits in Numbers:

Reduce AOG and turnaround time by 20-35%

Save $5-15 million annually per site by avoiding losses and rework

Achieve ROI with a payback period of less than 1 year

As one of the top 5 leaders in Aerospace put it about KINEXON: “We set a one-year ROI threshold, which KINEXON helped us meet. Beyond cost savings, the solution transformed our materials management. The team now automates tracking and monitors expiration of freezer materials — precisely managing usage time and impacting efficiency.”