Aircraft and ships announce themselves over the air, and volunteers with cheap receivers write it all down. That gives you movement history for most civil traffic and, through registries, a path to ownership. The cost: the data is self-reported by the vehicle, so it is exactly as truthful as its operator chooses. The beginner error is chasing the wrong identifier — tail numbers, callsigns, vessel names and MMSIs all change, while ICAO hex codes and IMO numbers largely don't. Resolve to the durable identifier first and everything downstream survives a rename.

N…

G-…

D-…

Full breakdown of which identifiers are permanent and which aren't is in the identifier reference.

Aircraft equipped with ADS-B Out broadcast their own GNSS-derived position about once a second, unencrypted. Anyone with a receiver hears it. The aggregators are networks of volunteer receivers, so coverage is a map of where hobbyists live, not where aircraft fly.

Three fields matter and are commonly confused:

Aircraft that transmit Mode S but not ADS-B position can still be located by multilateration, where several receivers compare signal arrival times. That needs several receivers hearing the aircraft at once, so it degrades badly at low altitude and vanishes outside dense coverage.

National registries map a registration to a registered owner: the FAA registry for numbers, the UK CAA register for , equivalents elsewhere. The data-source catalogue lists the ones worth knowing.

Expect a legal entity, not a person. Registered owners are routinely trusts, single-purpose LLCs, leasing companies, or bank trustees. In the US this is structural: registration requires US citizenship or qualification, so foreign owners commonly use an owner trust with a domestic trustee. Offshore registries — the Isle of Man, Aruba, Bermuda, the Cayman Islands, San Marino — largely serve this market, and their prefixes are a signal in themselves. A corporate shell isn't a dead end; it's a handoff to .

Registrations are also recycled. A freed tail number can be reissued to a different airframe, so an old track or photo tied to that registration may be a different aircraft. Check the registry's history for the mark and date every claim.

AIS looks like the maritime ADS-B and differs in the one way that counts: the transponder is crew-operated. Position is GNSS-derived, but switching it off is a switch on the bridge, and much of the payload is typed by hand.

Going dark is the finding. A vessel that switches off its transponder, or transmits a position contradicted by imagery, is doing something it doesn't want attributed — behaviour central to sanctions-evasion and dark-fleet work. Before you call it, exclude the benign causes: no receiver in range, satellite revisit gaps, VHF collisions in congested water, and equipment failure all produce identical-looking holes.

AIS is also spoofable — there's no authentication in the protocol, so positions can be fabricated wholesale, and vessels have been observed apparently sailing overland or appearing in two places. GNSS jamming near certain coastlines corrupts the positions of ships behaving honestly. A track is a claim about a position, not an observation of one.

Terrestrial reception is line-of-sight VHF, so coastal only. Satellite AIS fills the open ocean but samples on orbital revisit rather than continuously, struggles where many transmissions collide in one footprint, and is generally a paid tier.

IMO number is the permanent hull identifier and survives sale, rename and reflag — precisely why evasive operators rename and reflag but can't shed it. MMSI is issued by the flag state and changes on reflag, so a new MMSI against the same IMO is a reflag event with a date. Names change freely.

Flag choice is analytic information. Open registries — flags of convenience — sell registration to owners with no national connection, and a hull moving through a succession of small open registries with weak enforcement reputations is a pattern. Port state control inspection databases record detentions and deficiencies by IMO number and are one of the few independent checks on a vessel's real condition.

Ownership records distinguish registered owner, beneficial owner, commercial manager, technical manager and charterer — frequently different entities in different jurisdictions, with the registered owner often a one-ship company. Take it to and .

Never grade an AIS gap as "went dark" unless you can show coverage existed there at the time — for instance, that other vessels were reported nearby throughout the gap. That check separates the finding from the guess.

Objective: test a claim that a company jet flew executives to a jurisdiction they said they'd never visited.

Start with the registration from a press photo. It resolves to an ICAO hex, but the first tracker shows no history at all — an instructive dead end: the aircraft is on a privacy programme and that site honours the suppression. A community aggregator built on unfiltered volunteer feeds has the same hex with two years of tracks.

Those show a repeated home base and four trips into the region in question. Two have a clean position log; the other two drop out over water for hours, which is coverage, not evasion. The registry lists a Delaware LLC as owner, so ownership proves nothing about who flew — that goes to .

Graded: presence at the destination airport on two dates is probable on tracking data alone, and becomes confirmed for one date when a spotter photograph of the aircraft there, geolocated, turns up. Who was aboard remains unknown, and is reported as unknown.

Receiving these broadcasts is passive and lawful in most jurisdictions — they are unencrypted transmissions intended for public reception — though radio regulation varies, so check locally before building a receiver. The tracking sites are a different matter: scraping them generally breaches their terms, and their historical archives are licensed products. Use the APIs and free tiers as offered.

Registry data often carries reuse restrictions and sometimes includes an individual owner's home address. That remains personal data under GDPR and comparable regimes — don't republish it because a registry printed it. Authorities have moved toward letting owners withhold personal details; treat that as a legitimate choice, not an obstacle to route around.

Sanctions work has hard edges: vessels are designated by IMO number, and dealings with a designated vessel or its operators carry strict liability in many jurisdictions, so check current designations rather than memory. Tracking a private individual's aircraft, as opposed to a company's or a public figure's in their public capacity, sits close to the line — have a defensible objective before you start.