To get a correct answer to your original question, start at post #10.
To wit, no radar system needed. Is my reasoning correct?
Partly. It has never been the case that civilian aircraft should have to use their own radar to avoid collision. It happens, however, that weather radar will actually paint other aircraft once you are at reasonable height.
With all aircraft now using transponders to identify themselves, is there an on board system today that maps where other planes are in the vicinity around a given plane? If so, how far out? Does the transponder also flash FLs?
Yes, out to around 30 nm. It is called TCAS. FL information is available on some installations.
Also at night, is it standard practice to fly dark? I know Air Force One frequently does, and it was reported KAL 007 also was dark -- no wing or tail lights whatsoever, but that could have been Soviet propaganda to help justify the downing of that aircraft.
No.
