Track Planes and Ships

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.

Triage: which identifier do you have?

You have	Resolve to	Why
Tail number / registration (N…, G-…, D-…)	ICAO 24-bit hex	Registration is reassigned when the aircraft is sold or re-registered; hex follows the current registration but is what the trackers key on
Flight number or callsign	The specific airframe for that leg	Callsigns are per-flight and get reused daily by different aircraft
ICAO hex	Nothing — you're already there	The durable aircraft selector, as broadcast
Vessel name	IMO number	Names change with sale and with evasion; the hull doesn't
MMSI	IMO number	MMSI is a radio identity issued by the flag state and is reissued on reflag
IMO number	Nothing — you're already there	Permanent for the life of the hull
A photo of the vehicle	The visible identifier, then the above	Spotter photo archives index by registration and by name

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

[identifier reference](reference/identifiers.md).

Aircraft: how ADS-B actually works

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:

• ICAO 24-bit address — six hex characters, assigned by the state of

registry from a country-allocated block. It's the address in the protocol,

and it changes only on re-registration. This is your selector.

• Registration (tail number) — painted on the airframe, assigned by the

national registry, changes with ownership or country. Trackers derive it from

the hex via lookup tables, which is why a newly re-registered aircraft

shows the old registration on some sites and the new one on others.

• Callsign — what's transmitted for this flight. An airline flight number

for commercial traffic, usually the registration for general aviation, and

sometimes an operator's own designator. Per-flight and meaningless as a

long-term selector.

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.

The gaps that matter

• Oceans, polar routes and sparsely populated regions have no terrestrial

receivers. Coverage there needs satellite-based ADS-B, which not every

aggregator has and which is usually a paid product. A transatlantic flight

disappearing mid-ocean is normal, not a finding.

• Military and state aircraft frequently don't broadcast, broadcast

intermittently, or use identifiers that don't resolve to a registry entry.

Absence proves nothing about their activity.

• Privacy programmes. The FAA's Limiting Aircraft Data Displayed programme

lets an owner request their aircraft be withheld from the feed aggregators

receive. Privacy-address schemes separately allow eligible aircraft to

broadcast a temporary alternate ICAO address instead of the assigned one,

breaking the hex-to-registration link for its duration. Mechanisms also exist

for withholding owner details from public registry search.

• Aggregators honour blocking differently. Suppression works by filtering

at the data-distribution layer, so a network built on independent volunteer

feeds can show an aircraft another network hides — and policies change,

including when a site changes ownership. Check more than one, and record

which you used and when.

Ownership, and the trust problem

National registries map a registration to a registered owner: the FAA registry

for N numbers, the UK CAA register for G-, equivalents elsewhere. The

[data-source catalogue](reference/data-sources.md) 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 who-really-owns-it.

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.

Vessels: how AIS differs, and why that matters

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.

• Class A transponders are mandatory for larger commercial and passenger

vessels under international convention, transmit at higher power and update

frequently. Class B is voluntary and lower-power — small craft and

fishing boats are patchily covered at best.

• Static data (name, IMO, callsign, dimensions, ship type) is configured at

installation and is usually reliable.

• Voyage data (destination, ETA, draught, navigational status) is typed by

the crew each voyage and is wrong constantly: stale destinations, joke

entries, blank fields, wrong port codes. Treat it as a hint — except draught,

where a reported change between two positions with no port call in between is

evidence of a ship-to-ship transfer.

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.

Vessel identity and ownership

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 who-really-owns-it and x-ray-a-company.

Where this lies to you

• Coverage is not truth. No data means no receiver heard it; over most of

the planet's surface a gap is the default state.

• The vehicle is the source. Position comes from the aircraft's or ship's

own navigation system. Both can be wrong, and AIS can be deliberately false.

• Aggregator disagreement is informative. Different receiver networks,

blocking policies and registry snapshots. When two sites disagree about an

aircraft's identity, that usually points at a recent re-registration or a

suppression.

• Registry data is a snapshot. Registries update on paperwork, not on sale,

and lag. A current extract doesn't prove who controlled the vehicle last year.

• Identifier collisions. Registrations get reissued; MMSIs are reused,

duplicated and fabricated; vessel names aren't unique at all.

• Historical tracks are a paid feature. Free tiers show a short window. If

a track matters, capture it now.

• An airframe is not a passenger. Aircraft fly empty, fly staff, and get

chartered out. Placing the vehicle says nothing about who was aboard.

Grading a finding

• Confirmed — the position is corroborated by an independent source of a

different type: imagery showing the vehicle there and then, a port call in an

authority record, a photograph geolocated via geolocate-from-pixels, a

filing or notice. For identity, a dated authoritative registry entry.

• Probable — a consistent multi-receiver track from a reputable aggregator

with nothing contradicting it, or ownership from one registry that agrees

with a secondary commercial database.

• Unconfirmed — a single-receiver or single-aggregator track, any position

from a vehicle already suspected of spoofing, voyage-data fields, an inferred

destination, or a gap called intentional without excluding coverage and

equipment causes.

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.

Worked example

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 who-really-owns-it.

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.

Pivots

You now have	Take it to
Registered owner entity, trust, or one-ship company	who-really-owns-it, x-ray-a-company
A named individual owner or director	find-anyone
Operator's website or domain	recon-a-domain-passively, who-owns-this-domain
A photo of the aircraft or vessel	geolocate-from-pixels, find-the-original-image, secrets-in-file-metadata
Removed registry page or deleted operator site	read-deleted-pages
Registration, hex, IMO or MMSI as a search string	google-like-a-spy
Movements tied to a person's posts	pattern-of-life-from-socials
Fleet, owner and charterer relationships	graph-the-network
Sanctions or shipping chatter in forums and channels	find-leaks-in-the-wild

Legal and ToS

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.