ADS-B / Mode S message availability by region

% of aircraft in the region for which at least one message of the type was received 0 % → 100 %

Message type	Parameters carried	USAn=8,298	Canadan=297	Europen=4,965	Australian=253	Korean=46	Japann=383	S.American=162	African=130
ADS-B Extended Squitter1090ES downlink, DF17/18 — broadcast by the aircraft, no interrogation needed
Identification TC 1–4	callsign, wake/emitter category	95.8	97.0	97.3	97.6	97.8	94.3	97.5	92.3
Airborne position TC 9–18, 20–22	lat/lon (CPR), baro altitude (TC9–18) or GNSS altitude (TC20–22), NIC, SIL	100	100	100	100	100	100	100	100
Surface position TC 5–8	ground position, surface movement speed, ground track (needs airport-level receiver coverage)	3.2	3.7	2.1	6.7	0	3.1	3.1	3.1
Velocity TC 19	groundspeed, track, vertical rate, geometric–baro altitude offset, NACv	99.7	100	99.7	99.6	100	99.5	99.4	100
vertical rate source: barometric	VS flagged as barometric source	76.9	78.8	85.3	39.1	78.3	58.0	72.8	82.3
vertical rate source: GNSS	VS flagged as GNSS source	28.1	21.5	13.0	60.5	21.7	41.5	26.5	17.7
Target state & status TC 29	selected altitude (MCP/FMS), selected heading, QNH setting, nav modes (AP/VNAV/approach)	82.9	86.9	92.5	49.4	82.6	68.9	73.5	90.8
selected altitude	MCP/FMS target altitude	81.8	85.2	92.0	48.6	82.6	68.7	72.2	90.8
selected heading	MCP heading bug	56.9	69.7	61.7	31.6	60.9	51.2	39.5	53.1
QNH	barometric pressure setting	81.1	86.5	91.9	47.8	82.6	68.7	73.5	90.0
Operational status TC 31	ADS-B version, NACp, GVA, SDA, NIC-A, antenna/system flags	95.9	98.7	98.4	64.0	80.4	67.6	76.5	91.5
Mode S surveillanceelicited by ground SSR / Mode S / WAM interrogators — presence maps interrogator activity, not equipage
Comm-B replies DF 20/21	any ground-interrogated Comm-B reply (altitude / identity + 56-bit register payload)	19.9	44.1	97.1	83.4	97.8	93.0	0.6	83.8
Mode A squawk DF 5/21	4096-code transponder squawk in identity replies	44.5	34.0	98.4	87.7	97.8	93.0	1.2	94.6
EHS Comm-B registersDF20/21 payloads — BDS register inferred heuristically by readsb
BDS 4,0 selected vertical intention	MCP/FMS selected altitude, barometric pressure setting	2.1	16.5	88.4	63.2	93.5	54.0	0	57.7
BDS 5,0 track & turn	roll angle, true track, groundspeed, track angle rate, TAS	2.8	29.0	88.8	74.3	97.8	88.8	0	67.7
BDS 6,0 heading & speed	magnetic heading, IAS, Mach, baro altitude rate, inertial vertical velocity	2.9	30.0	90.7	76.3	97.8	88.8	0	66.2
MeteorologicalBDS 4,4 routine air report — only where interrogators request it (readsb build patched to print it)
BDS 4,4 met report	wind speed/direction, static air temperature; pressure, humidity, turbulence fields	0.1	0	12.4	1.2	0	0.3	0	0.8
measured wind	wind speed + direction fields valid	0	0	9.9	0.4	0	0	0	0
static air temperature	SAT field valid	0.1	0	12.4	1.2	0	0.3	0	0.8
ACASactive resolution advisories — absolute aircraft counts (rare events)
RA broadcasts BDS 3,0 / DF16 / TC28-2	active RA: advisory type, complements, threat identity	2	0	3	0	0	0	0	0

How to read this

This table shows what our receiver network hears, not what aircraft are equipped with. It was measured by replaying the RT raw ADS-B dumps (the same per-message data the workbench uses as its raw source) through the readsb decoder and counting, per aircraft, which message types appeared.

Survey windows: 03:00–03:10Z, 12:00–12:10Z and 18:00–18:10Z (UTC, 2026-08-23), chosen to catch each region's daytime traffic. An aircraft observed in two windows counts once per window. Aircraft are assigned to a region by their mean decoded position within a window; 17.7% of observed aircraft had no position decode (mostly aircraft heard only via Mode S replies or too few messages) and are excluded from the regional columns.
Feeder-network bias: percentages reflect RT feeder density and receiver placement. A low number can mean thin coverage (few receivers, aircraft heard only briefly at long range) as much as absent transmissions — South America and Africa in particular are sparsely covered, so read their columns as "what a typical received aircraft yielded", from small samples.
Mode S / EHS rows depend on the ground infrastructure, not the aircraft. Comm-B replies (DF20/21, BDS 4,0 / 5,0 / 6,0, BDS 4,4) are only transmitted when a ground SSR/Mode S interrogator (or WAM system) asks for those registers. Europe, Japan and Korea interrogate EHS heavily; the USA essentially does not. An aircraft showing no EHS data over the USA will typically produce full EHS data as soon as it enters European-style airspace.
BDS register inference: Comm-B replies do not label which register they carry — readsb infers BDS 4,0/5,0/6,0/4,4 heuristically from field plausibility. Rates are right in aggregate but individual replies can be misclassified; treat the EHS and BDS 4,4 rows as close estimates.
Mode A squawk (DF5/21 identity replies) likewise appears only where ground interrogators actively ask for Mode A/identity.
ACAS RA row: absolute aircraft counts, not % — genuine resolution advisories are rare events. Counted only where the RA payload (BDS 3,0, DF16 coordination reply or DF17 TC28/2 broadcast) contained an active RA/RAC indication.
Sources: this survey covers the RT raw ADS-B (raw) feed — per-message data from our own feeder network. The Aggregated ADS-B (agg) source merges additional upstream providers and therefore has different (wider) positional coverage, but carries only the merged state vector, not the per-message detail surveyed here.

Region definitions

Bounding boxes (lat, lon): USA 24–49 N, 125–66 W plus Alaska; Canada 49–72 N, 141–52 W; Europe 36–72 N, 11 W–40 E; Africa 35 S–35 N, 18 W–52 E; South America 56 S–13 N, 82–34 W; Australia 45–10 S, 112–154 E; Korea 33–39.5 N, 124–130 E; Japan 30–46 N, 128–146 E. Aircraft outside all boxes (620 positioned observations) are not shown.