Is it possible the descending traffic experienced RA and the cruising traffic only TFC advisory? I mean and the cruising traffic should have RA. Or not?
In
most cases, only one of the conflicting aircraft will receive an RA.
That's because the shape of the RA protection area is highly elongated (it's not a circle) so it is possible that an RA will be triggered in one aircraft but not (yet) in the other. Chances are, the aircraft first receiving the RA will respond to it, such that the other aircraft never gets an RA.