G-650 has been out lately (including right now)under GLF40.
flightaware.com/live/flight/GLF4 … /KSAV/KVLD
Gulfstream mixes different flight numbers and A/C types, so also search for flights by operator under “GLF”, or look at activity at KSAV for scheduled flights.
You never know where they may show up!
Some of the flight test people have a call sign, not always assigned to a particular airplane. I did my Lear 60 training before the simulator and it was that way with the flight safety instructors, they got to use a Lear xxx call sign.