SIC 3728 — Aircraft Parts and Auxiliary Equipment, NEC
Official OSHA SIC Manual Definition
Establishments primarily engaged in manufacturing aircraft parts and auxiliary equipment, not elsewhere classified. This industry also includes establishments owned by manufacturers of aircraft parts and auxiliary equipment and primarily engaged in research and development on aircraft parts, whether from enterprise funds or on a contract or fee basis. Establishments primarily engaged in manufacturing or assembling complete aircraft are classified in Industry 3721; those manufacturing aircraft engines and parts are classified in Industry 3724; those manufacturing aeronautical instruments are classified in Industry 3812; those manufacturing aircraft engine electrical (aeronautical electrical) equipment are classified in Industry 3694; and those manufacturing guided missile and space vehicle parts and auxiliary equipment are classified in Industry 3769. Establishments not owned by manufacturers of aircraft parts but primarily engaged in research and development on aircraft parts on a contract or fee basis are classified in Services, Industry 8731.
Description & Classification
SIC code 3728 representing 'Aircraft Parts and Auxiliary Equipment, NEC' is an industry category in the Standard Industrial Classification (SIC) system under U.S. OSHA and Federal procurement registers.
Modern NAICS Crosswalk
Trace the modern equivalent classifications in the 2022 North American Industry Classification System (NAICS) database:
- NAICS 336413 - Other Aircraft Parts and Auxiliary Equipment Manufacturing (via SIC1987:3728→NAICS1997:336413→2002:336413→2007:336413→2012:336413→2017:336413→2022:336413)
- NAICS 332912 - Fluid Power Valve and Hose Fitting Manufacturing (via SIC1987:3728→NAICS1997:332912→2002:332912→2007:332912→2012:332912→2017:332912→2022:332912)
- NAICS 541714 - Research and Development in Biotechnology (except Nanobiotechnology) (via SIC1987:3728→NAICS1997:54171→2002:541710→2007:541711→2012:541711→2017:541714→2022:541714)
- NAICS 541713 - Research and Development in Nanotechnology (via SIC1987:3728→NAICS1997:54171→2002:541710→2007:541711→2012:541711→2017:541713→2022:541713)
- NAICS 541715 - Research and Development in the Physical, Engineering, and Life Sciences (except Nanotechnology and Biotechnology) (via SIC1987:3728→NAICS1997:54171→2002:541710→2007:541712→2012:541712→2017:541715→2022:541715)
- NAICS 336411 - Aircraft Manufacturing (via SIC1987:3728→NAICS1997:336411→2002:336411→2007:336411→2012:336411→2017:336411→2022:336411)
Classification Details
| SIC Code | 3728 |
|---|---|
| Industry Title | Aircraft Parts and Auxiliary Equipment, NEC |
| Division | Division D: Manufacturing |
| Major Group | Major Group 37: Transportation Equipment |
| JSON Endpoint | View as JSON · API → |
| Source / Verified | US Census 1987 SIC Concordance / 2026-08-08 |
SIC vs NAICS Compliance & Common Mismatches
Legacy SIC code 3728 classifies commercial operations based on primary end-product or service output under the 1987 federal framework. In contrast, modern 2022 NAICS codes group establishments based on production process inputs.
When submitting public disclosures to SEC EDGAR or determining OSHA workplace safety log recordkeeping exemptions (29 CFR Part 1904), rely strictly on the official OSHA 4-digit SIC classification rather than an automated commercial translation.
💡 Expert Guidance: SIC to NAICS Conversion
Common Compliance Mistake: Many contractors and B2B analysts confuse legacy 4-digit SIC codes like 3728 with modern 6-digit NAICS codes. Ensure that you use the correct active 2022 NAICS code (e.g. from the crosswalk below) when submitting representations on SAM.gov, as federal contracting officers only accept modern NAICS codes.
Related Pages & Tools
Further regulatory reference links for legacy SIC code 3728:
- SIC Codes Complete Compliance Guide — Detailed history and active legal applications of the SIC classification framework.
- Why Legacy SIC Codes Persist Guide — How credit systems and the SEC still rely on SIC metadata.
- SIC ↔ NAICS Crosswalk Tool — Trace industrial code conversions dynamically.
- SIC 3728 to NAICS Crosswalk — Bidirectional mapping to modern NAICS codes (Aircraft Parts and Auxiliary Equipment, NEC).
- SIC Major Group 37 Hub — View other legacy industries in this business division.
Frequently Asked Questions (FAQ)
What industry sector is represented by legacy SIC code 3728? ▾
Legacy SIC code 3728 represents 'Aircraft Parts and Auxiliary Equipment, NEC', categorized under Division Division D: Manufacturing and Major Group Major Group 37: Transportation Equipment. The Standard Industrial Classification (SIC) system was developed in the late 1930s.
What is the modern 2022 NAICS equivalent for legacy SIC 3728? ▾
Legacy SIC code 3728 maps to the modern 2022 NAICS industry classifications: NAICS 336413 (Other Aircraft Parts and Auxiliary Equipment Manufacturing), NAICS 332912 (Fluid Power Valve and Hose Fitting Manufacturing), NAICS 541714 (Research and Development in Biotechnology (except Nanobiotechnology)), NAICS 541713 (Research and Development in Nanotechnology), NAICS 541715 (Research and Development in the Physical, Engineering, and Life Sciences (except Nanotechnology and Biotechnology)), NAICS 336411 (Aircraft Manufacturing). Mappings are resolved transitively across successive updates to handle splits.
Why do credit agencies and banks still reference legacy SIC code 3728? ▾
Registries like Dun & Bradstreet, insurance underwriters, and private platforms retain SIC code 3728 because their historical financial risk data and scoring models are indexed using the legacy 4-digit SIC framework.
Does the SEC EDGAR system allow searching public filings by SIC 3728? ▾
Yes. The SEC Division of Corporation Finance assigns a primary 4-digit SIC code to public companies. You can search the EDGAR database using SIC code 3728 to group reporting peer firms.
How do OSHA safety recordkeeping rules apply to SIC code 3728? ▾
Under 29 CFR Part 1904 safety regulations, OSHA references legacy SIC codes including 3728 to determine if a physical establishment is required to maintain daily injury logs (Form 300) or is partially exempt.
What is the structural difference between SIC 3728 and NAICS codes? ▾
SIC code 3728 classifies establishments based on their final product output or market destination (what they sell), while modern NAICS codes classify them based on production processes and inputs (how they work).
What are the typical business activities classified under legacy SIC 3728? ▾
Typical business activities classified under legacy SIC 3728 are the operations associated with 'Aircraft Parts and Auxiliary Equipment, NEC'. Mapped modern NAICS codes can be referenced for specific current examples.
Is legacy SIC code 3728 uniform across all 50 U.S. states? ▾
Yes, the Standard Industrial Classification (SIC) system, including code 3728, was published as a federal standard and remains uniform nationwide. It is still referenced by various state workers' compensation boards and departments of labor.
Sources & References
- U.S. Department of Labor (OSHA): OSHA Standard Industrial Classification (SIC) Manual — Code 3728
- U.S. Census Bureau: 1987 SIC to 2022 NAICS Concordance Tables
- Federal Reserve Board: Industrial Production & Capacity Utilization Classifications
- Internal Revenue Service (IRS): Schedule C Principal Business Activity (PBA) Industry Concordance
- Office of Management and Budget (OMB): Standard Industrial Classification Systems Governance