Ground-receiver coverage is uneven
Mountains, distance and antenna placement can create gaps, especially at low altitude. An aircraft may reappear once it enters range of another receiver.
Oceanic coverage depends on satellite or partner feeds
Services with space-based ADS-B can show aircraft far offshore, while others may interpolate between known points or display less detail.
Privacy programs can suppress identifying information
Some operators request that registration or flight details be limited in public feeds. Depending on the platform, the aircraft may be hidden, anonymized or displayed without owner information.
Certain government and military flights are filtered
Security policies can restrict public display even though the aircraft remains visible to appropriate aviation authorities.
A transponder issue can affect public reception
If ADS-B output is unavailable or not required, public tracking may become less precise. Controllers can still have other surveillance sources depending on the airspace.
The map should not be used to infer an emergency by itself
A missing icon is a data-availability event, not proof of trouble. Official airline, airport and aviation-authority information is more reliable for determining the status of an actual flight.
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