I think it is rather interesting that an aircraft can be flying around inside the Port Moresby Control Zone pretty much on the approach path to runway 14, and go un-noticed.
Regardless of Transponder and/or ADSB (if fitted) being turned off, would there not be a primary paint.
It's about time CASA PNG just told operators if you want to fly in PNG you must have ADSB and serviceable and switched ON at all times. Probably would enhance safety.