How MRO Shops and Operators Buy Aviation Parts

Updated October 14, 2026

How MRO parts buying differs from other aerospace purchasing

In aviation maintenance the person installing a part, not the seller, has to determine that it is eligible, so an MRO buyer is really buying evidence: a release document, a traceable record trail and a part that matches both. FAA Advisory Circular 20-62E puts it directly: the installer must determine that an article is eligible for installation before returning the product to service, and continued airworthiness is the owner or operator's responsibility.

That changes how a repair station or operator should run a purchase. Price and lead time still matter, but a part with a gap in its paperwork is worth very little to an installer, however good it looks. The regulatory background, Part 21 production approvals, PMA under 14 CFR 21.303 and the uses of FAA Form 8130-3, is laid out in our aviation and MRO library page. This page is about the buying: which release document to ask for, how to compare OEM, PMA and DER repaired options, what changes under AOG pressure, and what to write on the purchase order.

Release documents: FAA Form 8130-3 and EASA Form 1

For most new and overhauled components, the release document you want is an FAA Form 8130-3 or an EASA Form 1, and you need to check which release block was completed, not just that a tag exists. Both forms have a production side and a maintenance side, and the two make different statements.

The EASA Form 1 instructions say the statements in blocks 13a and 14a do not constitute installation certification, and that where the installer works under a different authority, the installer must make sure that authority accepts items from the authority named in block 1. Acceptance depends on bilateral agreements and each authority's policy.

The U.S. and EU bilateral is where this bites repair stations. EASA states that it accepts used components from a U.S. based repair station only with a dual release on the 8130-3, completed in blocks 14a to 14e, and that new components are accepted under a separate Technical Implementation Procedure. EASA's Maintenance Annex Guidance governs the used side; Change 9 took effect on October 8, 2024. If your customer operates EASA registered aircraft, put "dual release required" on the PO for overhauled and repaired units.

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OEM, PMA and DER repaired parts: what each one is

OEM, PMA and DER repaired describe different routes to an eligible part, and all three can be legitimate; the question is whether your operator, maintenance program and customer accept the route. The table below shows how buyers compare them.

A DER is a private engineer the FAA designates to approve engineering data in a defined area. 14 CFR 183.29 lists the categories, among them structural, powerplant, systems and equipment, radio, engine and propeller representatives, each acting within limits the FAA sets. The DER signs FAA Form 8110-3 to record a finding of compliance. FAA training material on the form explains that the DER either approves the data, when it is within the DER's authority, or recommends approval, in which case a separate FAA approval is still needed. Approving data for major repairs takes a special delegation listed on the DER's letter of authorization, explained in FAA Order 8110.37.

Two practical points. A DER approves the repair data, not the physical part; the repair itself is done and released by an appropriately rated repair station. And if the aircraft is registered outside the United States, ask early whether that authority accepts the DER data, because acceptance is not automatic. Many operators also set their own policy on PMA and DER repaired parts through their maintenance program, and lease agreements can restrict them at return. Check those rules before you compare prices.

AOG: what changes and what must not

When an aircraft is on ground, speed becomes the priority but the eligibility rules stay exactly the same, so AOG buying is about removing delay from everything except the paperwork check. AOG is also when unapproved parts are most likely to get through, because the seller who answers first is not always the seller with the records.

What speeds an AOG order:

• A complete part identity in the first message. Part number with dash number, acceptable alternates from the illustrated parts catalog, aircraft type and serial or registration, and the condition you will accept.
• The release requirement stated up front. 8130-3 production or maintenance release, dual release if needed, or manufacturer certificate of conformance for standard parts.
• Exchange or outright decided before quotes. Exchange often ships faster because a serviceable unit is already on the shelf somewhere.
• Delivery details. Ship-to station, after-hours receiving contact, and whether the part can go counter to counter or by courier.
• Who approves. One person who can accept a quote and an alternate part number at any hour.

What does not change: receiving inspection still matches the part, the data plate and the release document before the part goes on the aircraft. A quick check of serial number, part number and release block at the door takes minutes and is the cheapest insurance an AOG buy has. Our receiving inspection checklist is a usable starting point.

AS9120 distributors and traceability to the last certified source

Buy through distributors that can trace each part back either to the production approval holder or to the last certificated person who returned it to service, and treat a distributor's own certificate as a statement about the order, not about airworthiness. AC 20-62E is specific on both points.

For used parts, AC 20-62E says the data used to identify a part must be traceable to a person authorized to perform and approve maintenance for return to service under Part 43, and that the records must contain at least the data required by 14 CFR 43.9. It also lists the kinds of traceability a seller may be able to show, including parts produced by a production approval holder under a TC, PC, PMA or TSO authorization, standard parts from a named manufacturer, parts shipped under direct ship authority, and parts with removal records traceable to a U.S. certificated aircraft signed by an appropriately certificated person.

The AC also includes a note every buyer should remember: when a noncertificated person certifies that it is shipping the correct part, the only thing it states is that the part number agrees with the purchase order, not that the part is acceptable to the FAA. That is why the documents behind the distributor's certificate matter more than the certificate itself.

AS9120 certification, and accreditation under FAA AC 00-56, tell you the distributor runs a quality system built for this work. Neither one makes every part it sells eligible. Our guide to buying from AS9120 distributors covers the distributor types and the trace documents to require, and the material certs and traceability guide explains how lot data starts at the source.

Unapproved and suspected unapproved parts

If a part's origin, documents or condition do not support eligibility, stop, segregate it with its paperwork, and report it to the FAA as a suspected unapproved part instead of quietly returning it to the seller. The FAA runs a Suspected Unapproved Parts program under FAA Order 8120.16, and AC 21-29D explains how to detect such parts and report them on FAA Form 8120-11; the library page linked below covers the reporting route.

Patterns MRO buyers see most:

• An 8130-3 whose serial number, part number or signer does not match the part, the data plate or the issuing organization
• Overhauled units with no work order or teardown record behind the release
• Life limited parts whose back-to-birth record has a gap, or whose cycles cannot be reconciled
• Parts from salvaged aircraft or parts subjected to an accident, fire or sudden stoppage, presented as serviceable
• Standard hardware with only a distributor certificate and no manufacturer certificate or lot

Keep the part, packaging and documents together until the question is resolved. Our counterfeit parts avoidance page covers the controls that apply on defense contracts, and the aviation and MRO library page lists the advisory circulars and the reporting form.

Rotables and exchange

Rotables are serialized, repairable components such as pumps, actuators, starters, generators, avionics units and wheels, and they are usually bought one of three ways: outright, on exchange, or repaired and returned. The right choice depends on how fast you need a serviceable unit and whether your own core is repairable.

Condition codes on a quote are seller shorthand, so read them against the documents. AC 20-62E gives meanings for some of the words: overhauled means disassembled, cleaned, inspected, repaired as necessary, reassembled and tested to approved or acceptable data; surplus parts should show traceability to an FAA approved manufacturing procedure; and as is means the condition is unknown. As removed describes a unit as it came off the aircraft and says nothing about whether it works. What makes a rotable installable is the release document from a certificated person and the records behind it. For rotables with time limits, ask for time and cycles since new and since overhaul, the last shop visit report and, for life limited parts, the complete back-to-birth records. Missing records cannot be recreated later.

Exchange terms deserve attention. Disputes usually come from the core: a core rejected as beyond economical repair, a missing data plate, or a core that arrives without its removal tag. Write the core conditions on the PO so both sides judge the core against the same terms.

What to put on an MRO purchase order

An MRO PO should state the part, the acceptable condition and the exact release document, so the seller cannot meet the order with paperwork you would reject at receiving.

1. Part number with dash number and revision, plus any interchangeable alternates you accept, from the illustrated parts catalog or the operator's approved list
2. Aircraft or engine type, and the registry, so eligibility can be checked
3. Condition accepted: new, overhauled or serviceable, and whether PMA or DER repaired parts are acceptable
4. Release document: 8130-3 production or maintenance release, dual FAA and EASA release where needed, EASA Form 1, or manufacturer certificate of conformance for standard parts
5. Traceability: to the production approval holder, or to the last certificated person who returned the part to service, with the 43.9 records for used parts
6. For time controlled and life limited parts: time and cycles since new and since overhaul, and back-to-birth records
7. Transaction type: outright, exchange with core terms, or repair and return with workscope
8. Shelf life and storage data for elastomers, sealants and other dated items
9. Packaging and preservation, including caps and plugs on fluid ports and ESD packaging for avionics
10. Export classification where the part is going outside the United States; see export shipping and Incoterms
11. A clause requiring the seller to notify you of any nonconformance or suspected unapproved part finding on the lot

Where Aerospace Sourcing fits for MRO buyers

We are a sourcing service, not a parts distributor. We do not hold inventory, publish prices or claim to be an authorized or franchised distributor for any manufacturer. For an MRO request we search traceable sources, compare quotes on condition, release document and trace, check the paperwork against your PO before shipment, and deliver with a certificate of conformance and the source release documents.

We cannot make a PMA part, approve repair data or return anything to service; those take FAA approvals and certificated repair stations. Where the item will never be installed on an aircraft, such as GSE, tooling, test fixtures or shop equipment, we can have it made to your drawing; see obsolete aerospace parts and reverse engineering. If the same program needs credentialed people as well as parts, our contract technicians page explains how those requests are filled.

Send an MRO parts request

If you have an AOG, a rotable to exchange or a hard to find part, send it through the obsolete and hard to find parts form. Include the part number with alternates, aircraft type, the condition and release document you will accept, and whether you need a dual release. Those details let us discard quotes that would fail your receiving inspection before they reach you. A person replies within one business day, and rush requests are prioritized.

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Part, quantity and date are enough to start. Drawings and the mutual NDA follow by reply, and controlled programs never send technical data through this site.

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Questions

Related

• Sourcing Obsolete Aerospace Parts Safely
• How Do You Buy Safely From Aerospace Parts Distributors?
• How to Buy Obsolete Parts Without Buying Counterfeits
• Sourcing Contract Technicians for Aerospace Programs

Sources

• FAA AC 20-62E with Change 1, Eligibility, Quality and Identification of Aeronautical Replacement Parts
• EASA: Form 1 completion instructions (production and maintenance release blocks)
• EASA FAQ: dual release on FAA Form 8130-3 under the EU and U.S. bilateral agreement
• EASA: U.S. and EU Maintenance Annex Guidance (Change 8 copy; confirm the current change, Change 9 took effect October 8, 2024)
• Cornell LII: 14 CFR 183.29, designated engineering representatives
• FAA: compliance findings and FAA Form 8110-3 (designee training material)
• FAA Notice N 8110.111, DER approval of repair data
• FAA AC 21-29D, Detecting and Reporting Suspected Unapproved Parts
• FAA Voluntary Industry Distributor Accreditation Program (AC 00-56)
• Cornell LII: 14 CFR 145.1, repair station applicability