“Aircraft N888KG shut off transponder after take off. Saw another article that this is a common occurrence in this area due to mountains. Personally, I watch a handful of private jets taking off and landing from my office window and it is common for it to be off.”
Keep in mind this is all gossip and speculation:
If in controlled airspace the transponder must be on and have altitude reporting. ADSB is intertwined but separate. Only authorized flight without ADSB is military.
“”I watch a handful of private jets taking off and landing from my office window and it is common for it to be off.”””
You can tell that by looking at an airplane out of your office window?