Okay, this is going to be a little bit longer than average.
Please feel free to correct any assumptions or unrealistic hypothesis before answering.
The FAA mandates part 135 and 121 carriers to have TCAS II installed in every aircraft (if certain conditions are met), but TCAS is not mandated for GA aircraft nor private jets (Does this still apply? most likely.)
Now to my questions:
1- If you are in an IFR flight plan, does that mean you are in flight following (or at least getting traffic advisories) automatically or you still need to ask for it? is there any chance that you don’t get it?
2- If it is clear and an airliner is flying VFR bellow 18,000F for a short trip, is it still required to file IFR flight plan or it would be a VRF flight plan.
3- Let’s assume an airline pilot in-flight is not in contact with ATC like having the wrong radio frequency (or any other reason), How would she avoid a collision with a conflicting private jet - merging from 8 o’clock at the same altitude - which has no TCAS compatible transponder?
4- For two piston GA aircraft, see and avoid is realistic, but for two conflicting jets, I think the odds of survival are slim. with that been said, in the absence (or malfunction) of the TCAS, is there any other “Human free” alternative advisory?
Sorry for the long list, I hope you enjoy answering!