Glossary

The words a trading desk uses, defined plainly.

Alternate part number: An alternate part number is a different part number approved as interchangeable with the one requested, for example a newer dash number, an OEM equivalent, or a PMA part. Interchangeability is defined by the manufacturer's Illustrated Parts Catalog and related documentation, never by guesswork. Checking alternates is a routine quoting step, because a desk that only searches the exact number requested misses stock it could legitimately offer.
AOG (Aircraft on Ground): AOG (Aircraft on Ground) is the highest-priority situation in aviation maintenance, where an aircraft is grounded and cannot fly until a specific part is sourced and installed. Every hour of downtime can cost an operator from 10,000 to over 100,000 dollars depending on aircraft type, so an AOG request expects an answer in minutes, not hours. Most parts suppliers run a dedicated 24/7 AOG line, and buyers pay premium prices for immediate availability.
Condition codes (SV, NE, OH, AR): Standard tags describing the state of an aircraft part. SV is serviceable, NE is new, OH is overhauled, and AR is as removed. The condition drives both the price and which certificates travel with the part.
Exchange: An exchange is a transaction where the buyer receives a serviceable unit immediately and returns their removed unit, the core, to the seller, paying an exchange fee plus any repair costs on that core. The buyer gets the aircraft flying without paying the full purchase price, which matters when a single rotable can cost six figures. In an outright sale, by contrast, the buyer keeps the part and pays the full price with no core return.
Human-in-the-loop (quoting): Human-in-the-loop quoting is a workflow where software prepares the quote, parsing the RFQ, matching inventory, and suggesting a price, but a human trader reviews and approves it before anything reaches the customer. The approach combines the speed of automation with the judgment of an experienced trader, who stays accountable for price, condition, and paperwork. Tools like aersyn.ai apply this model, where the system drafts and the trader decides.
ILS (Inventory Locator Service): ILS (Inventory Locator Service) is one of the main online platforms where aircraft parts suppliers list inventory and buyers search for parts and send RFQs. Operating since 1979, it connects thousands of trading companies, airlines, and repair stations worldwide. For many parts desks, ILS and similar platforms such as PartsBase generate a large share of the daily inbound RFQ volume.
PO (Purchase Order): The buyer's commitment to purchase at the quoted terms. Reconciling the returned PO against the original quote, line by line, catches price and quantity gaps before anything ships.
Quote win rate: Quote win rate is the percentage of quotes sent that convert into purchase orders. In aircraft parts trading, typical win rates run between 5 and 20 percent depending on inventory depth, pricing, and response speed. Because a desk can send hundreds of quotes a month, a few points of win rate translate directly into six figures of annual revenue, which makes it the headline metric of quoting performance.
RFQ (Request for Quote): A buyer's request for a price and availability on one or more aircraft parts, usually sent by email with part numbers, conditions, and quantities. A busy trading desk can receive hundreds to thousands of RFQs a month, and the ones answered fastest tend to win.
Rotable: A rotable is an aircraft part that can be repeatedly removed, overhauled, and returned to service, such as landing gear, hydraulic pumps, or avionics units. Rotables carry a serial number and a full service history, and they hold most of the value in an aftermarket inventory. They contrast with expendables, which are replaced rather than repaired, and consumables like seals or fasteners, which are used up in a single installation.
Speed-to-quote: Speed-to-quote is the time between receiving an RFQ and sending the priced quote back to the buyer. In aircraft parts trading, buyers typically send the same RFQ to ten or more suppliers and shortlist the first few responses, so quotes sent within the first hour win disproportionately often. Cutting this delay from hours to minutes is the core metric that quoting tools such as aersyn.ai are measured on.
Trace: Trace is the chain of paperwork that documents where an aircraft part comes from and who certified it, typically back to an airline, a repair station, or the manufacturer. Key documents include the FAA 8130-3 and EASA Form 1 release certificates, along with removal records and non-incident statements. A part without acceptable trace sells for a fraction of its certified equivalent, because most operators are not allowed to install it.