When the ACMI Aircraft Goes AOG: Availability, Substitution and the Contract
AOG stands for "aircraft on ground": an aircraft that cannot fly because of a technical problem. In an ACMI lease, maintenance is the lessor's job, so an AOG is the lessor's problem to fix. But it is your schedule that suffers, and your passengers or cargo that wait.
What happens next depends almost entirely on the contract. These are the clauses that matter.
Guaranteed availability
The contract should state the percentage of scheduled flights the lessor commits to operate, often called dispatch reliability or guaranteed availability. For a modern aircraft with a good operator, a high figure is normal. Ask:
What percentage is guaranteed?
How is it measured: per month, per season, per flight?
What happens if the lessor falls below it?
A guarantee without a consequence is only an intention.
Substitute aircraft
If the aircraft is grounded, will the lessor provide another? The contract should say:
Whether a substitute is required, or only "reasonable efforts"
How fast it must arrive, for example within 24 or 48 hours
What size is acceptable: the same type, a similar seat count or payload, or anything available
Who pays for positioning the substitute and any extra costs
A smaller substitute with fewer seats may mean you have to refuse passengers. Agree in advance whether a substitute of a different type is acceptable and at what rate.
Response to short delays
Many AOG events are fixed in hours, not days. The contract should cover:
How quickly the lessor sends engineers and parts
Who pays for passenger care (hotels, meals, rebooking) during delays
When a delay becomes a cancellation for billing purposes
Minimum hours and rate abatement
This is where the money is. If you have agreed to pay for a minimum number of block hours per month, what happens when the aircraft cannot fly?
Are the minimum hours reduced for the days the aircraft is unavailable?
Or are they carried forward, so you have to fly them later?
Is there a rate reduction if availability falls below the guarantee?
Without a clear clause, you may be paying the monthly minimum for an aircraft that spent a week on the ground.
Planned maintenance
Scheduled inspections are not AOGs, but they also take the aircraft away. The contract should say:
How much notice the lessor must give
How long the aircraft can be away, and how often
Whether a replacement is provided during planned maintenance
Whether the minimum hours are reduced during that time
Ask for the maintenance forecast for the lease term before signing. A heavy check or an engine event falling in your peak season is worth knowing about in advance.
A simple checklist for your contract
Guaranteed availability percentage and how it is measured
Substitute aircraft: obligation, response time, acceptable type and cost
Delay handling and passenger care costs
Minimum hours: reduced, suspended or carried forward during AOG
Rate abatement below the guarantee
Planned maintenance notice, duration and replacement
Maintenance forecast for the whole term
How we help
Jetvice arranges ACMI leases directly with operators and reviews these terms on every deal. Email info@jetvice.net or see our aircraft leasing page.
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