Why are military aircraft on flight radar?

Any aircraft flying under air-traffic control in controlled airspace needs a transponder so that radar can identify it, and since 2020 both the FAA and EASA have required ADS-B Out, which broadcasts GPS position, altitude and identity roughly once a second. Military transports, tankers, VIP jets and patrol aircraft routinely use airways alongside airliners, so they comply with the same rules. Sites such as Flightradar24 and ADS-B Exchange collect those broadcasts through networks of volunteer receivers, which is why a KC-135 or an A400M shows up like any Boeing 737.

Fighters and special-mission aircraft usually have a transponder too, but crews can select modes that omit position data, transmit only when needed for deconfliction, or turn the equipment off in a training area or a combat zone. Older military transponders send Mode S identity without ADS-B, which lets tracking sites estimate a position by multilateration when several receivers hear the same signal. Some operators ask commercial tracking services to hide certain airframes; Flightradar24 does so for aircraft owners on request, while ADS-B Exchange publishes everything its receivers hear.

Open tracks have made large deployments, evacuation flights and refuelling patterns visible to anyone with a browser. The armed forces accept this because broadcasting position in crowded skies is safer than not doing so, and because anything truly sensitive is flown with transmissions off or outside civil airspace. A track that disappears at a coastline or an exercise boundary is usually an aircraft switching to a discreet mode rather than a malfunction.