By AOG is a revenue event, not a maintenance event
A defect gets raised in the tech log. Engineering checks it against the Minimum Equipment List. If the item can be deferred, the aircraft flies with a placard and a repair clock running. If it cannot be deferred — or the deferral has already run out — the aircraft is Aircraft on Ground. AOG.
From that moment the aircraft does not fly again until a serviceable unit, released on an authorised release certificate (an EASA or UK CAA Form 1, or an FAA 8130-3), is fitted and signed off by a licensed engineer. That chain is fixed. Most of it is regulatory, and none of it can be rushed.
What can be compressed is the bit in the middle: the physical movement of a part from wherever it is sitting right now to the bay where an engineer is standing with the panel already open. Sourcing the part is procurement. Getting it into a hand is logistics — and it is often the biggest single block of dead time in the whole event. It is also the block you can actually do something about.
What an hour on the ground actually costs
Every operator has its own per-hour AOG figure, and operators generally treat it as commercially sensitive. The components of it are not mysterious, though, and they stack fast: lost sector revenue on a cancelled or delayed rotation. Crew running out of hours and finishing in the wrong place. Hotels and repositioning. Downstream rotations that unravel across the rest of the day because one tail is missing. Rebooking passengers onto other carriers. Passenger compensation obligations, where they apply. A missed slot. Cargo that has to be rebooked onto someone else's aircraft.
On a freighter, it is the load that does not move plus the customer who does not wait. On a business jet, it is a charter cancelled outright.
The practical consequence for the person on the phone at 02:00 is simple. The question is almost never "what does a dedicated vehicle cost". It is "what does another three hours on the stand cost" — and for most operators the second number is the bigger one by a wide margin. That is the whole logic of AOG logistics in one line.
The part is nearly always already in the country
This is the bit that surprises people outside aviation. In a great many UK AOG events, the component is not being manufactured from scratch or flown in from another continent. It exists. It is sitting in an operator's main-base store, a spares pool, a distributor's warehouse near an airport, an MRO's stock, a lessor's consignment inventory, or on a sister airline's shelf — and an AOG desk that does exactly this all day will usually find it quickly.
So the part is found. And then, very often, nothing happens for hours.
Because what is missing at that point is not a component. It is a vehicle and a driver, going one way, starting now. The gap between "we have located it, it is at a supplier near Manchester" and "it is in the engineer's hand at Luton" is where the money burns. Nothing in a scheduled parcel or pallet network is designed to close that gap, because those networks were never built for it. They were built for volume, and AOG is the opposite of volume.
Why a network cannot do this — and a dedicated vehicle can
A parcel or pallet network is a hub model. Collect during the day, trunk overnight, sort, deliver the next morning. That is an efficient design for volume — and structurally wrong for AOG, because the consignment has to sit in a sorting operation before it can move onward. There is a cut-off. There is a trunk. There is a hub. Each one is a place your part can be delayed, missorted or damaged, and none of them care that an aircraft is on stand.
A dedicated vehicle removes the whole model. One vehicle, one job, your consignment the only thing on board. Straight from collection to delivery: no shared loads, no consolidation, no sorting hubs, no overnight trunking. The ETA becomes a function of distance and traffic rather than a cut-off time, and you can watch the vehicle on live tracking and forward that to the hangar.
The vehicle is also sized to the job rather than to the network. A boxed avionics LRU goes in a small van. An engine stand, a wing panel or crated GSE does not — that is a Luton with a tail lift, a 7.5-tonne, an 18-tonne, or at the extreme a 13.6m articulated lorry.
Rotables, tooling and the return leg nobody books
An AOG movement is rarely one-way, and the second leg is the one that gets forgotten in the panic.
Rotables: the unserviceable unit comes off the aircraft and has to go somewhere — back to the repair shop, to the pool provider, or to the exchange supplier. Those exchanges normally carry a core-return window. Miss it and the commercial position changes: what should have been a repair charge starts turning into the outright price of the unit. That return is a real, dated logistics obligation, and it is worth booking at the same time as the outbound rather than remembering it a fortnight later.
Tooling and ground support equipment: borrowed jigs, torque equipment, borescope kits, engine stands, lifting gear. On plenty of AOG events the constraint is not the part at all — it is a piece of tooling on the wrong side of the country, on loan, due back.
The operational point: if the swap is happening on arrival, say so when you book. A driver waiting while the unit comes off is cheaper and faster than a second mobilisation the following day.
The last 500 metres: hangar, cargo gate, airside
An airport is not an address, and "Heathrow" is not a delivery point. The maintenance side, the cargo terminals and the landside stores can be miles apart, with different gates, different security, different opening hours and different people.
Before a vehicle rolls, pin down four things:
- The exact delivery point — hangar number, gate, cargo shed, stores door — not just the airport.
- A named receiver with a mobile number who is genuinely on shift when the vehicle arrives. Not the day-shift planner's desk phone.
- The references the receiving site will ask for: works order, PO, AWB, part number, and the release certificate travelling with the unit.
- Whether the handover is landside to a person who takes it through, or genuinely requires an airside pass and an escort. Assume landside unless someone has confirmed otherwise — an escort is arranged by the site, not by the driver.
The worst outcome in an AOG job is a van parked at a barrier at 02:40 with the correct part on board and nobody answering the number on the paperwork. That is a wholly avoidable failure, and it is avoided at booking, not at the gate.
Cut-offs, night running and the 03:00 call
Much line maintenance is a night business. The aircraft is worked between last arrival and first departure, which means the part is often needed for a 04:00 fit, not a 09:00 one. That is precisely the window in which scheduled networks are closed, sorting, or trunking.
A dedicated vehicle has no cut-off to miss. The constraint is getting a vehicle to the collection point, not catching a network timetable — which is why AOG work sits naturally with a 24/7/365 operation rather than an office that opens at eight.
One genuine constraint is worth understanding: drivers' hours. Goods vehicles over 3.5 tonnes fall under drivers' hours and tachograph rules, which cap continuous driving and require breaks. Smaller vans sit under a lighter domestic regime. That is one practical reason a long overnight AOG run across the country often goes on a van rather than a larger vehicle — and why a genuinely long leg on a heavy vehicle needs to be planned around rest requirements from the outset. Better to know that at booking than to discover it at 03:00 on the M6.
Cross-border: it is the paperwork that grounds the van
UK to EU AOG movements add a customs step at both ends, and the failure is almost never the driving — it is the documentation.
What has to exist before wheels reach the border: an export declaration and an import declaration, the commodity code and value, an EORI number, the authorised release certificate travelling with the part, and — for a GB departure through a port that operates it — a goods movement reference under GVMS. Tooling and equipment going out temporarily and coming back are often handled on an ATA Carnet rather than a full export. Civil aircraft parts can attract duty relief in certain circumstances; your broker or customs agent will know what applies to the specific commodity code, and 02:00 on an AOG is not the moment to guess.
The operational trick is to run the paperwork in parallel with the vehicle, not in sequence. A driver can be collecting and heading for the crossing while the declarations are being lodged. Doing it the other way round — documents first, then dispatch — routinely costs more hours than the crossing itself.
What to have ready when you call
AOG calls move faster when the caller already has the operational facts to hand. Before you dial, gather:
– Collection address, site contact and mobile, and whether the goods are ready now or still being picked and packed.
– What it actually is: dimensions, weight, packaging (loose box, ATA case, crate, engine stand) and whether it needs a tail lift or a forklift at either end.
– Delivery point: hangar or gate number, named receiver, their mobile, and the references they will ask for.
– The time the engineer genuinely needs it — the fit time, not a comfort buffer.
– Any dangerous-goods content. Fire-bottle squibs, chemical oxygen generators and lithium batteries are all regulated, and declaring them up front changes what can be carried and how. Discovering it at collection stops the job.
With that in hand, a dedicated vehicle can be assigned to the collection point and your consignment moves directly to the aircraft — tracked, with no other freight on board.
For an AOG movement, call Transol Sameday on 0330 311 2323. We run 24/7, 365 days a year.
