AOG and the clock: sourcing parts under pressure

Here is what usually happens next.

The director of maintenance calls the guy. Not a guy. The guy, the one he has used for eleven years, who picks up at odd hours and has never burned him. The request goes out. Everyone goes to bed. At 9:20 the next morning a price comes back. It is high. Everyone can feel that it is high. Nobody has time to find out how high, because the alternative to accepting it is arguing about it while the airplane sits there. The purchase order goes out at 9:34.

That is not incompetence, and it is not laziness. It is arithmetic. The DOM has one aircraft down, a crew to reposition, a shop to coordinate, an owner or a charter client to call, and one phone. Running a real market search is a job, and at that moment he already has one.

The number that actually matters is not the part

Start with what the day costs, because that number is the one that makes every other decision make sense.

If you are flying Part 91, the cost is trips. A canceled board meeting, a principal on a commercial flight out of a hub he specifically bought an airplane to avoid, and a slow erosion of the internal argument that the aircraft is worth what it costs. Hard to invoice, easy to feel.

If you are flying Part 135, the cost has a dollar sign on it. Midsize charter rates in 2026 run roughly $4,300 to $7,000 per hour, most operators enforce a daily minimum somewhere around two to two and a half billable hours, and a grounded aircraft does not just lose the trip it was on. It loses the trip after that, and the repositioning leg that was going to pay for the deadhead. Two days down on a moderately booked aircraft is not hard to add up into the range of $30,000 to $50,000 of billable time that will never be recovered, before you count subcharter to cover the trip you promised, crew hotels, and the client who quietly starts calling somebody else.

You will see much larger numbers quoted. Widely repeated industry figures put airline AOG at $10,000 to $150,000 per hour. Do not use them. Those numbers describe a network unraveling: missed connections, downstream cancellations, passenger compensation, slot exposure. A single aircraft flight department does not have a network to unravel. Estimates aimed at business aviation are more useful and more sober, generally landing around $15,000 to $50,000 per day in direct cost for a mid size corporate jet.

The part is rarely the expensive thing. The day is the expensive thing. Which is precisely why the part gets overpaid for.

Why AOG is where pricing discipline goes to die

Urgency and negotiation cannot occupy the same room. The moment a call opens with "we are AOG," the person on the other end knows three things: you need it today, you have not called anyone else yet, and you are not going to spend the next four hours shopping. There is no poker face available to you. The situation is the tell.

It is worth saying that the rush premium is often legitimate. Somebody is walking a shelf after hours, cutting paperwork that normally waits for morning, and driving a box to an airport for a counter to counter shipment. That is real work at a real cost, and AOG commentary commonly describes rush pricing running 50 to 200 percent over routine procurement.

The problem is not the premium. The problem is that you cannot tell a fair premium from an opportunistic one with a sample size of one, and one phone call is a sample size of one. The same urgency that makes price discovery valuable is the exact reason nobody performs it.

What a competent search actually looks like, hour by hour

Hour zero to one: define the requirement properly

More AOG searches go sideways here than anywhere else, and the failure is invisible until the wrong box arrives. Before anything goes out, you want the part number plus known alternates and supersedes, the next higher assembly, applicable service bulletin and airworthiness directive status, quantity, acceptable conditions in order of preference, aircraft registration and physical location, the delivery address and the person who will sign for it, and whether your repair station can accept a dual release tag or needs FAA release only.

That last one is not a detail. A part that arrives with the wrong release is a part that cannot be installed, which means you have spent the night and the money and are exactly where you started, except now it is Wednesday.

Hour one to three: work the pool in parallel, not in sequence

The distinction between a good search and a bad one is not effort. It is shape. A bad search is serial: call, wait, get a number, call the next one, wait. Each cycle burns an hour and by the third call the shipping cutoffs have started closing behind you.

A parallel search puts the same defined requirement in front of the entire reachable pool at once. That pool is wider than most departments use on a normal Tuesday: the OEM and authorized distribution, independent stocking distributors, exchange and rotable pools, the repair station you are already sitting in, and other operators of your type, who are frequently the fastest source in existence and almost never get asked.

Hour three to five: collect answers on the same axes

Price is one column out of six, and on an AOG it is not the most important one. The others are condition, the tag and who issued it, the physical location of the unit, the shipping cutoff and the realistic arrival time rather than the promised one, and core terms if the offer is an exchange.

Four quotes that each report a different set of facts are not four quotes. They are four conversations you now have to have.

Hour five onward: decide on time to airworthy

Not price. Not ship time. Time to airworthy, which is the moment the part is installed, signed off, and the aircraft is legal to fly. That clock includes the receiving inspection, the paperwork review, the install, the ops check, and the log entry. A part that lands at 6:00 a.m. and clears receiving at 6:30 beats a cheaper part that lands at 5:00 a.m. with a tag your inspector has questions about.

Condition codes, and why the cheapest tag is not always the fastest to airworthy

The two letter codes are shorthand for two things at once: what was physically done to the part, and what paperwork exists to prove it.

• FN and NE, factory new and new. Never used, no time or cycles, full certification and traceability, usually a manufacturer warranty. The expensive, boring, correct answer.
• NS, new surplus. Unused and never installed, but it has been sitting somewhere, sometimes for years, and it may not carry complete original OEM documentation. Date of certification, storage environment, and shelf life matter here, particularly on anything with seals, elastomers, or batteries in it.
• OH, overhauled. Disassembled, cleaned, inspected, repaired as required, reassembled, and tested to the component maintenance manual, then released by a certificated repair station. The closest thing to new that the used market offers.
• SV, serviceable. Inspected and found fit for installation, but not restored to new limits. It installs legally. It may have materially less life remaining than an overhauled unit.
• RP, repaired. A specific defect was corrected and the unit released. Narrower scope than an overhaul.
• AR, as removed. Taken off an aircraft in unknown, untested condition, with no maintenance release. Over the years AR has become a catch all for any used part without return to service paperwork.

Two of those deserve more attention than they usually get.

The serviceable versus overhauled decision is a life decision disguised as a price decision. A serviceable unit at $21,900 against an overhauled unit at $38,400 looks like a $16,500 win right up until the moment you realize you may be buying that same part again in eighteen months and paying a second AOG for the privilege. If you are selling the aircraft next spring, serviceable is obviously correct. If you are keeping it for six years, run the math on cost per remaining hour instead of cost per unit, and the answer often flips.

As removed, on an AOG, is almost never the answer no matter what the price says. An AR unit is not a part, it is a project. It has to be evaluated and certified before it can be returned to service, which means you have just inserted an entire repair station turn time into the middle of a grounding you were trying to end tonight.

The paperwork you still cannot skip at midnight

This is the section people skim. It is also the section that costs the most when it is wrong, because the damage is deferred.

FAA Form 8130-3, the Authorized Release Certificate, is the document that makes a part legally distinguishable from an unapproved one. It creates a documented chain from the approving entity to the installer. EASA Form 1 serves the same function and is accepted under the bilateral agreement between the two authorities.

One thing worth knowing about the form, because it trips up smart people: the bottom of it carries two separate certification blocks. One certifies that a new item conforms to approved design data. The other certifies that a used item has been approved for return to service after maintenance. Which block is completed tells you what the tag actually says, and it is not always the thing the listing implied.

Here is the part that makes this non negotiable rather than merely advisable. The FAA has been explicit for years that establishing the eligibility of a part for installation is the responsibility of the owner or operator, not the seller. Advisory Circular 20-62E says so directly, pointing at the maintenance responsibility rules in Parts 91, 121, 125, and 135. The broker who sold it to you at 11:40 at night is not the one holding that bag. You are. The FAA even publishes a guide, AC 20-154, for building a receiving inspection system, and if your operation does not have one written down, that is an afternoon of work that will eventually save you a very bad week.

A paperwork failure does not stop the airplane tonight. It stops it eight months from now, in a pre-buy, when a technical rep pulls the file and finds a tag nobody can substantiate. Then the part comes off, on your dime, and the transaction takes the delay.

Exchange, outright, or loan

Three structures, and the difference between them is where the cost and the obligation land.

• Outright. You buy it, you own it, there is no core to return and nothing outstanding. Highest number on the invoice, lowest number of future surprises.
• Exchange. You receive a serviceable unit now and send your unserviceable core back. Two common structures: a flat rate exchange, where the fee is the fee, and exchange plus repair, where you pay a fee now and the actual repair cost of your core later. The second one is where people get surprised, because that later number is not knowable when you sign.
• Loan or rental. A daily rate for a unit while yours is being repaired, and you get your own unit back. Sensible when your core is clearly repairable and you want that specific serial number returned.

The AOG nuance on exchange is worth stating plainly, because the industry markets it as the fast option and that is only conditionally true. Exchange is fast when the exchange unit is sitting on a shelf you can physically reach today. It stops being fast the moment it has to travel three time zones, and it carries a tail that outright purchase does not: a core return window, documentation requirements on the core, and a bill back if the core comes home beyond economical repair or does not come home at all. Cores that go missing become full price invoices four months later, long after everyone has stopped thinking about that Tuesday.

So on any exchange offer, ask three questions before you accept it: what is the core return window, what happens if the core is beyond economical repair, and what is the maximum I can end up owing.

The same part number, four ways

An illustrative comparison for a single rotable on a single evening. The numbers are constructed to show the shape of the decision rather than to quote a specific market.

The one phone call produces the first row and nothing else, and the first row looks perfectly reasonable when it is the only row. Laid out together, the picture is different. The independent distributor gets the aircraft airworthy roughly twelve hours sooner and costs $16,500 less, at the cost of remaining life you may or may not care about. The exchange is cheapest tonight and comes with a range attached, and that range is the actual price of the decision. The authorized distributor costs the most and is the only option that will never generate a phone call in ninety days.

There is no universally right answer in that table. There is only a right answer for your aircraft, your utilization, and how long you intend to own it. What is not defensible is choosing without seeing the other three.

Sometimes the right answer is the expensive part

A real search does not always find you a cheaper part, and any company that promises otherwise is selling something. Sometimes it finds a more expensive part that arrives eight hours sooner, and on a charter aircraft with two trips on the books, eight hours is worth considerably more than the price delta.

The point of running the search was never to win on price. It was to be able to see the trade and make it deliberately, which is a different thing entirely from making it by accident because one person answered the phone.

What VHMX does at 7:15 in the evening

Your director of maintenance should be managing the aircraft. Talking to the crew, working the MEL, coordinating the shop, planning the recovery, deciding what actually gets installed. That is where their judgment is worth the most money, and it is the one part of this nobody else can do.

What they should not be doing is dialing eleven suppliers and transcribing quotes onto a legal pad.

Send us the requirement once. Our specialists work the entire supplier pool in parallel while your DOM works the airplane. Options come back side by side on the same six axes: condition, tag and issuing authority, physical location, realistic time to airworthy, landed cost, and core terms. You pick. We coordinate the rest. Here is the full walkthrough of how that works.

Suppliers never see each other, and your tail number and your situation stay private. That matters more during an AOG than at any other moment in the ownership cycle, because "they are down and they are out of options" is a piece of market intelligence you should not be handing out for free at eleven at night.

One request out. The whole market worked at once. You see the options side by side and decide with information instead of adrenaline.

VHMX does not decide what part goes on your aircraft. Your director of maintenance and your repair station make that call, and they should. What we do is make sure they are choosing from the whole market rather than from the first person who answered the phone.

Sources and further reading: FAA Advisory Circular 20-62E, Eligibility, Quality, and Identification of Aeronautical Replacement Parts. FAA Advisory Circular 20-154, Guide for Developing a Receiving Inspection System. FAA Advisory Circular 21-29, Detecting and Reporting Suspected Unapproved Parts. FAA Form 8130-3 and FAA Order 8130.21. 14 CFR 91.403 and 135.413. Industry condition code references from Business Jet Parts, Skylink International, and C and L Aviation Group. 2026 charter rate ranges from published operator and broker rate guides.