NSN to part number: turning a 13-digit stock number into an RFQ line, and when military surplus may go on a civil aircraft
A National Stock Number identifies an item in the US and NATO supply systems — it does not identify a part on a seller's shelf. Aircraft parts sellers quote by part number and CAGE code, not by NSN, so an RFQ that carries only a 13-digit number usually comes back slow, or wrong. This guide explains what an NSN encodes, how to find the part numbers behind it with tools DLA itself publishes, how to write an RFQ line that a seller can act on, and — separately — what the regulations actually say about a part that reached you through military supply channels.
What the 13 digits actually encode
A National Stock Number (called a NATO Stock Number outside the US) is the 13-digit identifying number assigned to each "item of supply" in the US federal catalog, and in the NATO codification system that shares its format. It has two parts: a four-digit Federal Supply Classification (FSC) and a nine-digit National Item Identification Number (NIIN). The FSC groups the item with similar items into a class; the NIIN identifies the item itself. The first two digits of the NIIN are the National Codification Bureau (NCB) code of the country whose cataloging office assigned it — generally the country where the item was first codified, usually its country of manufacture — and the remaining seven digits are, in the federal regulation's word, "nonsignificant."
| Example NSN | FSC (4 digits) | NIIN (9 digits) | What it tells you |
|---|---|---|---|
5310-00-807-1474 | 5310 — Nuts and Washers | 00-807-1474 | Country code 00 is the United States; the last seven digits, 807-1474, carry no further meaning by themselves. |
The FSC on its own is only a category: 5310 covers every stocked nut and washer, not one part. The NIIN is what a database search actually keys on. Neither one is a manufacturer's part number, and neither one is a CAGE code — the five-character Commercial and Government Entity code that identifies the company that made or supplied the item.
One NSN, several part numbers
An NSN identifies an item of supply, not a manufacturer's catalog entry. The Defense Logistics Agency's own cataloging data cross-references each NSN to "reference numbers" — the manufacturers' and suppliers' part numbers recorded for that item — each tied to a CAGE code. A common hardware item can carry reference numbers from several manufacturers who all build to the same specification; a more specialized item may carry the original manufacturer's number plus the numbers assigned by an aircraft OEM, a government activity or a later manufacturing source. An NSN by itself does not tell you which of those numbers the seller in front of you can supply, or whether each of them is eligible for your aircraft. For a civil aircraft, that answer comes from your maintenance data — the illustrated parts catalog (IPC) and the type design behind it — not from a supply catalog.
In supplier quotes we received between mid-June and late September 2026 (about 126,000 quote lines, 15,900 part numbers), a number in the NSN format appeared in the part number or description on 1.19% of lines — 753 distinct part numbers. Standard hardware part numbers under the MS, NAS or AN systems were far more common: 25.6% of lines, 1,562 distinct numbers. See our guide to buying AN, MS and NAS hardware for what to ask when the part is standard hardware rather than a proprietary design.
Free ways to go from NSN to part number and CAGE code
DLA runs the authoritative NSN database, and it publishes a free public counterpart to its internal search tool:
| Tool | Who can use it | What it gives you |
|---|---|---|
| WebFLIS (Web Federal Logistics Information System) | Used primarily by DLA, the military services and US government-sponsored contractors; access only through controlled authentication (CAC, ECA or Federal Bridge) and a role requested in DLA's Account Management and Provisioning System (AMPS) | Online search of FLIS data — NSN, item name, reference/part numbers, CAGE codes — not open to the public |
| PUB LOG (Public Logistics Data) | Downloads are available to the US government, foreign military sales, other foreign national customers and the private sector — no subscription, no CAC | A free monthly download of the publicly releasable FLIS data, including the Master Cross Reference Data (MCRD) that ties NSNs, reference numbers and CAGE codes together, and the Management Data Interchangeability and Substitutability (MDI&S) data used to determine the interchangeability and substitutability of items of supply |
PUB LOG is not a one-box web search: DLA distributes it as a downloadable dataset with its own query application, updated monthly, and the download excludes service-unique data, proprietary data and NATO data, and NSNs that carry proprietary information are left out of the cross-reference. It is, all the same, the free and public route from an NSN to the reference numbers and CAGE codes DLA has on file for it, straight from the agency that assigns the numbers.
A number of private databases also let you type an NSN into a search box and get an instant result. We do not link them here — many are run by parts sellers, and results vary in how current and how complete they are. Treat a match from any third-party site as a lead to confirm, not as the part number and CAGE code you put on a purchase order.
Writing the RFQ line
A seller quotes a part, not a stock number, so the line should carry both, plus everything that changes the price and the answer time:
| Put on the line | Why |
|---|---|
| The NSN, if that is what your system holds | Lets the seller cross-check it against a part number, and search their own stock and supplier base by it |
| The manufacturer's part number and CAGE code, if you have them | This is what most sellers actually search and quote by; an NSN alone slows the search down |
| A description in your own words | Catches a mismatched cross-reference before it becomes a wrong shipment |
| Quantity, and unit of issue if it is not "each" | An NSN can be stocked by the box, the foot or the pound as much as by the piece |
| Condition you can accept: new, new surplus, overhauled, serviceable, as removed | The same NIIN can be quoted across a wide range of condition and price |
| The certificate you need: 8130-3, EASA Form 1, dual release, or a certificate of conformity | Name the one you need rather than leaving it to be assumed |
| Whether an alternate or superseded part number is acceptable | See the next section — say it explicitly rather than leaving it to be assumed |
For the rest of what a complete RFQ line should carry, see our guide to writing an aircraft parts RFQ and, once quotes come back, how to read what a supplier actually quoted.
Alternates: say what you will accept
Because one NSN can carry several manufacturers' reference numbers, and a specific reference number can itself have been superseded by a newer dash number, "the NSN" is not a single, fixed part any more than "the part number" always is. If your maintenance data allows more than one manufacturer's part for the position, say so on the RFQ — list the numbers, or write "alternates per IPC acceptable" if that is your source. DLA's interchangeability and substitutability data is a supply-management tool, not a basis for installing a part on a civil aircraft. Leaving it unstated does not get you a wider search; it gets you a quote against whichever single number the seller happened to match first. Our guide to alternate, superseded and interchangeable part numbers covers how to word that line and what "one-way" and "two-way" interchangeable actually mean.
Military surplus on a civil aircraft: what the rule actually says
An NSN is a supply-system identifier, not a production-approval basis, and the two questions are separate. Finding the right part number from an NSN tells you what to ask for. Whether a specific part in front of you — one that moved through military supply, or was released as government surplus — may go on a type-certificated civil aircraft is a different question, and the FAA's rules answer it narrowly.
The production rule: 14 CFR 21.9
Under 14 CFR 21.9(a), a person who knows, or should know, that a replacement or modification article is reasonably likely to be installed on a type-certificated product may not produce that article unless it is one of: produced under a type certificate; produced under an FAA production approval; a standard part manufactured to a government or established industry specification; a "commercial part" as defined in 21.1; produced by an owner or operator for maintaining or altering its own product; fabricated by an appropriately rated certificate holder with a quality system and consumed in a repair or alteration under part 43; or produced in some other FAA-approved manner. Having carried an NSN, or having come from a military source, is not on that list. What matters is which of those bases actually backs the specific part. Section 21.9 governs who may produce such parts; the decision to install one rests with the installer and the owner or operator, who must determine that the part is eligible before returning the aircraft to service (AC 20-62E, paragraph 8).
Section 21.9(c) does use the word "surplus" directly, but only for a narrow case, and as a restriction rather than a permission. For an aircraft type-certificated under §21.25(a)(2) (restricted category, for a type manufactured to the requirements of, and accepted for use by, the US Armed Forces) or §21.27 (a surplus aircraft of the US Armed Forces type-certificated in the normal, utility, acrobatic, commuter or transport category), a person may not sell or represent an article as suitable for installation unless it "was declared surplus by the U.S. Armed Forces" and "was intended for use on that aircraft model by the U.S. Armed Forces" — parts produced under a type certificate or an FAA production approval excepted. That concerns ex-military airframes flying under those specific type certificates; it says nothing that would make a military-surplus part eligible for an ordinary commercial or business jet.
FAA guidance on surplus parts: AC 20-62E
Advisory Circular 20-62E, Eligibility, Quality, and Identification of Aeronautical Replacement Parts (current through Change 1, dated September 14, 2018), defines surplus and addresses it directly. Its definitions section describes surplus as a "product, assembly, part, or material that has been released as surplus by the military, manufacturers, owners/operators, repair facilities, or any other parts supplier," adding that "these products should show traceability to an FAA-approved manufacturing procedure." Its paragraph on surplus parts is blunter about the risk:
"Parts obtained from surplus sources may be used, provided it is established that they meet the standards to which they were manufactured, interchangeability with the original part can be established, and they are in compliance with all applicable ADs. Such items, although advertised as 'remanufactured', 'high-quality', 'like-new', 'unused', or 'looks good', should be carefully evaluated before they are purchased. The storage time, storage conditions, or shelf life of surplus parts and materials are not usually known."
The same AC also asks that unusual origins be disclosed in the part's records: if a part came from a "noncertificated aircraft (aircraft without airworthiness certificate; i.e., public use, non-U.S., and military surplus aircraft)," that origin "should be so identified by some type of documentation (i.e., maintenance record entries, removal entries, overhaul records)."
What that means for an RFQ
- An NSN match is a starting point for sourcing, not proof of eligibility. Ask what production-approval basis under 21.9(a) backs the specific part offered — a type certificate, an FAA production approval, a standard-part specification, a commercial-part determination, or one of the other listed routes.
- Ask directly whether a part was released as government or military surplus, and for the documentation AC 20-62E describes: what standard it was built to, how interchangeability with the part you need was established, its AD status, and what is known about its storage history.
- 21.9(c) is a narrow rule, not a route to eligibility. It applies to specific ex-military aircraft type certificates, not to parts for an ordinary standard-category aircraft.
For what should travel with any part you buy — 8130-3, EASA Form 1, a certificate of conformity, and trace — see what certificates and trace come with each part.
One more check: export control
A part that reached the market through military supply channels may also be classified differently for export than an equivalent civil part. A part "specially designed" for a military aircraft can fall under ECCN 9A610 (the "600 series") on the Commerce Control List, or on the US Munitions List under the International Traffic in Arms Regulations, rather than under 9A991 or EAR99, where most civil aircraft parts sit. Which one applies turns on the "specially designed" analysis for that part — not on its NSN, and not on how routine it looks. Our export control guide for aircraft parts buyers covers EAR99, 9A991, the 600 series and ITAR, and what to ask the seller before you order.
Send the NSN, and whatever else you already have
Send your RFQ to [email protected] in the file you already have — Excel, PDF, a scan or the email body, five lines or five hundred — as is. If a line carries only an NSN, say so; if you also have a part number, CAGE code, acceptable alternates or a certificate requirement, add them — the more the line carries, the less there is to clarify. Your inquiry will be reviewed by a specialist within one business day.
Our client portal, RFQ Radar, keeps every quote, order and invoice in one place, with condition, certificates, lead time and ships-from country on every line.
Before you buy, check what certificates and trace come with each part. Aircraft on ground? See our 24/7 AOG desk.
Sources
- 41 CFR § 101-30.101-3, National stock number — e-CFR via Cornell LII (FSC, NCB code, NIIN).
- NATO Stock Number — Wikipedia (NCB country code list; 00 = United States).
- Product and Service Code (PSC) Manual — Acquisition.gov (FSC 5310, Nuts and Washers).
- PUB LOG® – Public Logistics Data — Defense Logistics Agency (what PUB LOG provides, access, MCRD and MDI&S; page read via Internet Archive snapshot of 16 March 2026).
- WebFLIS® – Web Federal Logistics Information System — Defense Logistics Agency (access requirements, AMPS registration; page read via Internet Archive snapshot of 30 January 2026).
- 14 CFR § 21.9, Replacement and modification articles — Electronic Code of Federal Regulations via Legal Information Institute, Cornell Law School.
- 14 CFR § 21.25, Issue of type certificate: restricted category aircraft — e-CFR via Cornell LII.
- 14 CFR § 21.27, Issue of type certificate: surplus aircraft of the Armed Forces — e-CFR via Cornell LII.
- AC 20-62E, Change 1, Eligibility, Quality, and Identification of Aeronautical Replacement Parts — FAA, 14 September 2018 (§ 6.h, definition of surplus; § 8, installer's eligibility determination; § 10.c, Unusual Circumstances; § 11, Surplus).
- 15 CFR part 774, Supplement No. 1 (Commerce Control List) — e-CFR via Cornell LII (ECCNs 9A610 and 9A991).