Callsign JST is Jetstar
WHAT AIRLINE IS JST?
JST is the ICAO three-letter callsign prefix for Jetstar. When a radio scanner, flight tracker or radar scope shows a flight like JST123 or JST45XY overhead, that's a Jetstar aircraft talking to air traffic control.
Spot one yourself: open the live scope, enter your postcode, and tap any blip whose callsign starts with JST for its type, registration, route and photo.