Aircraft parts glossary: the abbreviations on RFQs, quotes, purchase orders and paperwork

Before you look anything up: three rules for trade shorthand

Most of the abbreviations below are trade shorthand, not regulation. No rule defines NE, STK or ARO, and sellers use them slightly differently. Where a term does have a legal or standard meaning, such as an airworthiness directive, a life-limited part or an Incoterms rule, the definition below follows that source and the source is listed at the end.

• Same letters, different meaning. AR, TSO, FT and RP each have two common readings on the same kind of paperwork. When a term matters to the deal, ask the seller to write it out.
• An empty field is not a “yes”. A blank certificate column does not mean a certificate comes with the part, and a blank lead time does not mean stock.
• The quote is not the paperwork. A quote line that says “8130-3” or “trace to OEM” describes what the seller expects to send. What arrives is checked at receiving inspection.

0–9

8130-3 (FAA Form 8130-3, Authorized Release Certificate). The FAA's release document, also called the airworthiness approval tag. On a new part, block 11 reads NEW for an item that conforms to approved design data; after maintenance, the release names the work done. Which release your customer accepts is in FAA 8130-3 vs EASA Form 1 vs dual release, and how old a tag may be in aircraft part tag date.

121, 129, 135, 145 trace. A trace ending at a source certificated under that part of 14 CFR: a US air carrier (121), a foreign air carrier operating in the US (129), a commuter or on-demand operator (135), or a repair station (145). The number names the kind of source, not the source itself. See aircraft parts traceability.

A

AD (Airworthiness Directive). Under 14 CFR 39.3, a legally enforceable FAA rule applying to aircraft, engines, propellers and appliances. An AD can require a part to be inspected, modified or replaced, which is why AD status belongs in the paperwork for used rotables. See interchangeable part numbers.

ALT, alternate. A different part number offered in place of the one you asked for. An “alternate” on a quote is the seller's suggestion; only the IPC, a service bulletin or your engineering can make it an approved alternate. See alternate, superseded and interchangeable part numbers.

AN, MS, NAS (standard hardware). Part numbers defined by published government or industry specifications: AN (Air Force–Navy, as AC 20-62E expands it), MS (Military Standard) and NAS (National Aerospace Standard), among others, as in MS21042 nuts. Under 14 CFR 21.9(a)(3) such a standard part may be produced without an FAA production approval, and on receipt a certificate of conformity naming the standard is the usual paperwork. See AN, MS and NAS standard hardware.

AOG (aircraft on ground). An aircraft that cannot fly until a part arrives. On an RFQ it puts speed first, and the buyer may weigh a different condition, price or source against time. See AOG parts sourcing: the first two hours.

AR (as removed). A condition code: the part was taken off an aircraft or engine and nothing has been done to it since. It carries no release for installation and is typically bought as a core or for your own shop. In an IPC quantity column, AR usually means “as required”. See condition codes.

ARO (after receipt of order). Lead time counted from when the seller receives your purchase order, as in “7 days ARO”. It usually counts to ready or shipped, not delivered, and does not say whether days are calendar or business days. See aircraft parts lead time.

ATA chapter. The two-digit system number used in aircraft manuals and IPCs, for example chapter 32 for landing gear. Giving it on an RFQ line helps a seller find the right part when the description is short.

ATA Spec 2000. Airlines for America's e-business specification for parts; its procurement chapter covers quotation requests and responses, purchase orders, invoices and shipment messages. Condition codes are often called “Spec 2000 codes”, but Spec 2000 is a paid industry specification, not a regulation.

ATA Spec 106. Sources and Approved Parts Qualification Guidelines, an industry guidance document for airline parts quality programs, not a mandatory one. It includes a sample commercial certification form, and the “ATA 106 form” that many sellers issue with a part descends from it, in many local versions. See traceability.

ATA Spec 300. Airlines for America's specification for packaging airline supplies, with packaging and testing guidelines for repairable and expendable units, kits, hazardous materials and electrostatic-sensitive devices. “ATA 300 packing” on a PO asks for a container built to it.

B

B2B, back-to-birth. A records package that traces a part, usually a life-limited part, from its manufacture to today without gaps, so every hour and cycle is accounted for. See back-to-birth traceability.

BER (beyond economical repair). A shop finding that repairing a unit would cost more than it is worth. In an exchange, a BER core can trigger an extra charge, so the percentage and its base matter. See exchange and core charges.

C

CAGE code. A Commercial and Government Entity code: an identifier the Defense Logistics Agency assigns to a US commercial or government entity at a specific location; entities outside the US get an NCAGE code. Parts data uses it to name the manufacturer behind a part number.

CMM (component maintenance manual). The manufacturer's manual for testing, repairing and overhauling a component. An overhaul or repair is done to it, and a release often cites its revision. See what a release must say about the data used.

CoC, C of C (certificate of conformity or conformance). A statement from a manufacturer or distributor that a part conforms to its specification or order. AC 20-154A lists a CoC identifying the standard as the expected document for standard parts; for other parts a CoC alone is weaker than an 8130-3 or Form 1. A “Mfr CoC” is issued by the manufacturer itself, not a distributor. See which certificate to ask for and standard hardware.

Core. The unserviceable unit you send back in an exchange. It must match the part number and meet the core acceptance terms, or a core charge is billed, often much larger than the exchange fee. See exchange, core charge and BER.

CR (cycles remaining). For a life-limited part, the cycles left before its limit, sometimes at a stated engine thrust rating. Buyers often set a minimum, such as a number of cycles remaining at the PO date. See back-to-birth traceability.

CSN, TSN (cycles since new, time since new). The accumulated cycles and flight hours of a part since it was made. In 14 CFR 1.1, time in service runs from the moment an aircraft leaves the surface of the earth until it touches down at the next landing.

CSO, TSO (cycles since overhaul, time since overhaul). Cycles and hours since the last overhaul. Compare them with the overhaul interval, if the part has one; do not confuse this TSO with a Technical Standard Order.

Cure date. For elastomer parts such as O-rings, the date the rubber was cured, often given as a quarter and year. Shelf life is counted from it. See aircraft parts shelf life.

D

DAR (Designated Airworthiness Representative). Under 14 CFR 183.33, a person who may examine, inspect and test for the FAA and issue certificates within the limits the FAA sets, and who may charge a fee. “DAR 8130-3” on a quote means a release signed by a DAR, which can add cost and days. See the true cost of an aircraft part.

Dash number. The suffix after the base part number, as in -3 or -5. A different dash number can be a different part; it is not automatically interchangeable. See interchangeability.

DG, hazmat (dangerous goods, hazardous materials). Items regulated in transport: lithium batteries, oxygen generators, extinguisher bottles and squibs, many sealants and paints. A DG line needs trained packing and a declaration and may be barred from passenger aircraft; for chemicals, the transport section of the SDS (safety data sheet) tells you. An airline's own COMAT (company material) is not exempt. See dangerous goods in a parts order.

DOM (date of manufacture). When the part was made. It is not the tag date, and not the cure date. See tag date vs manufacture date.

Dual release. A maintenance release signed for both the FAA and EASA, by an organization holding both an FAA part 145 and an EASA Part-145 approval. It exists only on the maintenance side, not for new parts. See 8130-3, Form 1 and dual release.

E

EAR (Export Administration Regulations). The US Commerce Department rules, administered by BIS, that govern exports of most civil aircraft parts. See export control for US aircraft parts.

EAR99. The designation for an item subject to the EAR but not listed under any ECCN. BIS notes that such items usually need no license, but one can still be needed for certain destinations, end users or end uses.

ECCN (Export Control Classification Number). A five-character code on the Commerce Control List: a digit for the category, a letter for the product group, then three digits. Civil aircraft parts are often 9A991. See EAR99, 9A991 and ITAR.

EEI (Electronic Export Information). The export data filed in the Automated Export System for a US shipment. The Incoterm alone does not decide who files it: that depends on whether the export is standard or routed. See who files the US export.

Exchange (EXCH), outright, loan. In an exchange you receive a serviceable unit now and send your unserviceable one back as the core; the price is an exchange fee plus later charges. Outright is a straight sale with nothing sent back. A loan lends you a unit for a fee, usually per day, while yours is repaired. See aircraft part exchange.

EXW (Ex Works). An Incoterms rule: the seller makes the goods available to the buyer, typically at its own premises, and the risk passes to the buyer there; the seller does not clear the goods for export. Freight from that door is extra. See EXW, FCA or FOB.

F

FCA (Free Carrier). An Incoterms rule: the seller hands the goods to the buyer's carrier at the named place, and the risk passes there. Unlike EXW, the seller completes export formalities.

FN (factory new). New and unused, from the manufacturer or its authorized channel. Some sellers add an age limit to the term. See condition codes.

FOB (Free On Board). Under Incoterms 2020, a rule for sea and inland waterway transport only: the seller delivers once the goods are loaded on the vessel at the named port. On US parts quotes, “FOB origin” or “FOB + city” usually uses FOB in its US domestic sense and needs clarifying. See FOB on a parts quote.

Form 1 (EASA Form 1, Authorised Release Certificate). The EASA release document. A production organization approval holder issues it to state that a part was made to design data; maintenance organizations use the same form, and then block 11 reads overhauled, repaired, inspected/tested or modified. The UK CAA issues its own Form 1. See FAA 8130-3 vs EASA Form 1.

FT. Feet as a unit of measure, as with hose, wire or tape; on some condition columns, function tested. See UOM.

H

HTS code, Schedule B. The tariff classification of goods: the importing country's tariff heading sets the duty, and Schedule B is the US export classification. Civil aircraft parts may qualify for duty relief, but not automatically. See are aircraft parts duty-free?

I

IN (inspected, inspected/tested). A condition or release status: checked visually, functionally or on the bench to a stated standard, and not overhauled. See condition codes.

Incoterms. The International Chamber of Commerce's rules for where the seller delivers, where the risk passes and who does the export and import formalities; the current edition is Incoterms 2020. They do not set the price or the transfer of ownership. See Incoterms on an aircraft parts quote.

IPC (illustrated parts catalog). The manufacturer's catalog of an aircraft's or component's parts, with figure and item numbers, quantities and interchangeability notes. It is where you confirm a part number and its approved alternates. See interchangeability.

ITAR (International Traffic in Arms Regulations). The US State Department rules for defense articles on the US Munitions List. An ITAR part cannot simply be sold abroad like a civil one. See export control.

L

LLP (life-limited part). Under 14 CFR 43.10, any part for which a mandatory replacement limit is specified in the type design, the instructions for continued airworthiness or the maintenance manual; its life status is the accumulated cycles, hours or other limit. Engine disks are a typical example. See back-to-birth traceability for life-limited parts.

LRU (line replaceable unit). A component designed to be changed at the aircraft, such as a pump, valve, sensor or avionics box, rather than repaired in place.

LT (lead time). The time until the part is available to ship, usually in days ARO. It is not the time to your door. See lead time.

M

MLV (minimum line value). A floor per line item: a line priced below it is raised to it. Several cheap lines on one PO can each be raised. See minimum order charges.

MOQ (minimum order quantity). The fewest pieces the seller will sell, often a pack or reel size. Fifty rivets when you needed six is a minimum paid in parts. See the true cost of an aircraft part.

MOV (minimum order value). A floor for the whole order, in money. Written as a fee or “per transaction”, it is charged once per order or shipment, however many lines it holds, so price small lines with it applied. See minimum order and minimum line charges.

N

NE (new). Unused, with no time or cycles, and traceable to the manufacturer. The paperwork can be a manufacturer's release or a seller's CoC with trace, so ask which. See condition codes.

NFF (no fault found). A shop tested a returned unit and could not reproduce the reported fault. It often carries an evaluation fee. See warranty returns.

NIS (non-incident statement). A signed statement that a part was not involved in an accident or incident, often requested with used parts and LLPs. It is industry practice, not a regulatory requirement, and some parties prefer an incident/accident clearance statement. See non-incident and non-military statements.

NS (new surplus). Unused, but passed through other owners, such as an operator's excess stock. Tags on new surplus are often years old. See condition codes and tag date.

NSN (National Stock Number). The 13-digit identifier the US and NATO supply systems give an item of supply. One NSN can cover several manufacturers' part numbers, so it is not an IPC alternate. See why an NSN is not an IPC alternate.

NTE (not to exceed). A cap on a repair price that the shop may not pass without your approval. See repair or replace.

O

O&A (over-and-above). Charges on an exchange or repair beyond the flat price, for work the unit turned out to need. Ask for approval rules and a cap. See over-and-above charges.

OBF (out-of-box failure). A part that fails on installation or first test, before any real service. It is usually handled faster than an ordinary warranty claim. See out-of-box failure vs warranty claim.

OBO. On a listing or price, “or best offer”: the price is open to a counteroffer. In email it can also mean “on behalf of”, when a broker writes for another company. Ask which is meant.

OEM (original equipment manufacturer). The company that designed and makes the part, or its production approval holder. “OEM trace” or “OEM cert” means the paperwork reaches back to it.

OH (overhauled). Disassembled, cleaned, inspected, repaired as needed, reassembled and tested to approved data, usually the CMM, with a maintenance release. See condition codes.

P

PAH (production approval holder). The holder of an FAA production approval, which 14 CFR 21.1 says can be a production certificate, a PMA or a TSO authorization. A PAH's parts normally carry its markings.

PMA (Parts Manufacturer Approval). An FAA design and production approval for a replacement or modification part, often made by a company other than the original manufacturer; subpart K of 14 CFR part 21 governs it. Whether a PMA part is acceptable is your operator's or customer's decision. See PMA parts vs OEM.

P/N, PN (part number). The manufacturer's identifier for a part, including its dash number. Different spellings with dashes, spaces or slashes are one of the commonest reasons two quotes do not match. See comparing quotes from many suppliers.

PO (purchase order). Your written order to the seller, with part number, condition, quantity, price, certificate and delivery term. Its wording decides what the seller owes you. See what to put on an aircraft parts PO.

PPW (paperwork). The documents that come with a part: release certificate, CoC, trace, statements. “Full PPW” asks for all of it; say which documents you mean. See traceability.

R

Receiving inspection. The check of parts and paperwork on arrival, before stock is accepted. AC 20-154A describes what a receiving system should cover. See receiving inspection per AC 20-154A.

RFQ (request for quotation). Your request to one or more sellers to price a list of parts. The more precisely each line states condition, certificate and quantity, the more comparable the answers. See how to write an aircraft parts RFQ.

RMA (return material authorization). The seller's number authorizing a return. Most sellers will not accept a return without one. See the RMA process.

RO (repair order). An order to a shop to repair or overhaul your unit, as opposed to buying another. See repair or replace an aircraft component.

Rotable, expendable, consumable. A rotable is repaired or overhauled and returned to service many times and is tracked by serial number: a starter, a pump, a wheel. Expendables and consumables, such as hardware, seals, filters and sealants, are used up or discarded rather than repaired, and are usually bought new.

RP. To many sellers, repaired: a defect fixed and tested. To others, repairable: a unit that still needs a shop. Ask which. See condition codes.

S

SB (service bulletin). A manufacturer's notice recommending an inspection or modification. An SB can change a part number or its interchangeability; an AD can make it mandatory. See interchangeability.

Shelf life. How long an item may be stored before use, counted from its cure date or manufacture date. On an RFQ, ask for remaining shelf life, not just the total. See aircraft parts shelf life.

S/N, SN (serial number). The individual unit's identifier. For rotables and LLPs, the S/N on the tag, the data plate and the records must match.

Standard part. Per AC 20-154A, a part made in complete compliance with an established government or industry specification that is published so anyone may make it. See AN, MS and NAS standard hardware.

STK (stock). The seller has the part and can ship it quickly. It does not say whose shelf or which country, and stock can sell before your PO arrives. See what “stock” usually means.

Subject to prior sale. The quoted unit is not reserved for you and may be sold before your order is accepted. Ask for a hold time if it matters. See lead time.

SUP (suspected unapproved part). Per AC 21-29D, a part suspected of failing the criteria of 14 CFR 21.8 or 21.9, for example because of different finish, missing identification or altered paperwork. SUPs are reported to the FAA. See how to verify an aircraft parts supplier.

Superseded. Replaced by a newer part number. The new number may or may not be usable where the old one was. See superseded and interchangeable part numbers.

SV (serviceable). Used and found fit after inspection or test, not necessarily overhauled. Some sellers use SV for a unit repaired only for its reported fault. See condition codes.

T

Tag, tag date. The tag is the release certificate itself, such as an 8130-3 or Form 1; the tag date is the date it was signed. There is no regulatory maximum age, but many buyers set one. See aircraft part tag date.

TBA, TBD (to be advised, to be determined). The seller does not know yet: the lead time, price or certificate will be confirmed later. Treat it as unknown. See lead time.

TBO (time between overhauls). The interval, in hours, cycles or calendar time, at which a component or engine is due for overhaul. Hours since overhaul mean little until you compare them with it.

Trace. The documents that show where a part came from: the last certificated source and, ideally, the chain back to the manufacturer. A trace is a record of origin, not a release for installation. See aircraft parts traceability.

TSO (Technical Standard Order). Under 14 CFR 21.601, a minimum performance standard issued by the FAA for specified articles used on civil aircraft; a TSO authorization is a design and production approval for an article that meets one. Not to be confused with time since overhaul.

U

Unapproved part. Per AC 21-29D, a part that fails the criteria of 14 CFR 21.8 or 21.9, including counterfeit and intentionally misrepresented parts. See how to verify an aircraft parts supplier.

UOM (unit of measure). What one unit of the quoted price is. Common codes, set by convention rather than by any rule: EA (each), PR (pair), PK (pack), BX (box), KT (kit), RL (roll), FT (foot), IN (inch), M (meter), GL (gallon), QT (quart), LB (pound). A price per box set against a price per piece is a classic false bargain; ask how many pieces a pack or box holds. See why one part number gets very different prices.

USM (used serviceable material). Used parts released as serviceable, often from aircraft or engines being torn down. Condition, trace and remaining life decide their value. See obsolete aircraft parts.

W

Warranty. The seller's promise about a part's condition or performance for a period after sale, on its own terms. Periods, what voids them and who pays freight differ by seller, so read the terms before buying. See warranty returns.

Sources

• eCFR — 14 CFR 1.1, General definitions (appliance, time in service)
• eCFR — 14 CFR 21.1, Applicability and definitions (design approval, production approval)
• eCFR — 14 CFR 21.9, Replacement and modification articles
• eCFR — 14 CFR part 21, subpart K, Parts Manufacturer Approvals
• eCFR — 14 CFR 21.601, Technical Standard Orders: applicability and definitions
• eCFR — 14 CFR 39.3, Definition of airworthiness directives
• eCFR — 14 CFR 43.10, Disposition of life-limited aircraft parts
• eCFR — 14 CFR 183.33, Designated Airworthiness Representative
• eCFR — 15 CFR 734.3, Items subject to the EAR (EAR99)
• eCFR — 15 CFR 772.1, Definitions of terms as used in the EAR (export control document, EEI)
• eCFR — 22 CFR 120.1, General authorities (ITAR)
• Acquisition.gov — FAR 2.101, Definitions (CAGE code)
• Bureau of Industry and Security — Classify your item (ECCN structure, EAR99)
• Federal Aviation Administration — Order 8130.21J, Completion of FAA Form 8130-3 under Part 21 (25 September 2025)
• Federal Aviation Administration — AC 20-154A, Guide for Developing a Receiving Inspection System for Aircraft Parts and Materials (3 July 2024)
• Federal Aviation Administration — AC 20-62E, Eligibility, Quality, and Identification of Aeronautical Replacement Parts
• Federal Aviation Administration — AC 21-29D, Detecting and Reporting Suspected Unapproved Parts
• EASA — FAQ: EASA Form 1 as the Authorised Release Certificate of a POA holder
• EASA — FAQ: block 11 of EASA Form 1 after maintenance
• International Chamber of Commerce — Incoterms 2020: EXW or FCA
• International Chamber of Commerce — Incoterms 2020: FCA or FOB
• Airlines for America — Spec 2000, Gen 2 Procurement
• Airlines for America — Spec 300, Specification for Packaging of Airline Supplies
• Airlines for America — Spec 106, Sources and Approved Parts Qualification Guidelines
• Aviation Suppliers Association — Using the ATA 106 for Commercial Trace (ASA Commerce, vol. 8, issue 1, January 2000)
• Aviation Suppliers Association — Non-Incident/Accident Statement (NIS) and Incident/Accident Clearance Statements (ICS) (15 October 2015)
• Duncan Aviation — 16 important aircraft parts sales and core exchange terms (December 2018)
• Wikipedia — NATO Stock Number (structure of the 13-digit NSN)
• MG AVIATION TECH — offer lines from supplier quotes received between June and September 2026, aggregated; no prices or supplier names published.