By a former RPO/RSO for an international aviation MRO · Updated July 2026
Most repair stations and parts brokers are holding radioactive material right now and don't know it — because intact aviation devices arrive with no placards, and the federal license that attaches to them (10 CFR 31.5's general license) issues no certificate. Here is where Class 7 material actually lives in the fleet.
1. Self-luminous signs and dials — tritium (H-3). Exit signs, cabin placards, instrument dials, standby compasses. If it glows with the power off, it contains radioactive gas in glass micro-tubes. Intact, the external hazard is negligible; a broken tube indoors is the real risk. These typically ship as UN2911 excepted packages.
2. Counterweights — depleted uranium. Elevators, rudders, and outboard ailerons on legacy transport types. DU is "source material" under 10 CFR 40, regulated regardless of dose rate. The plating is the containment — never grind, drill, or sand one, and never, ever scrap one: steel mills run portal radiation detectors, and the trace-back ends at your dock.
3. Gauges and indicators — krypton-85. Some fuel-quantity and pressure instruments. Check the manufacturer's data sheet at receiving.
4. Ionization smoke detectors — americium-241. Lavatory and cargo-bay detectors on many types.
The moment a covered device enters your inventory, the general license attaches — automatically, with no application. Its duties are enforceable: obey every label instruction (the label is the license), perform any label-required tests with records, transfer only to authorized recipients with a paper trail, and report loss, theft, or damage on federal timelines. Anyone whose work affects the transport of these items also needs recurrent training — every 24 months under IATA if you ship by air, 36 months under DOT.