A week ago crew of A320 reported traffic on TCAS reciprocal 25NM.
At the moment the A320 was passing F325 for F360.
Traffic was a chopper at 2000ft. indeed reciprocal.
Can someone throw some light on how the TCAS picked up
this low level traffic?
Possibly the aircraft was receiving a TA only as the low flying aircraft was squawking with no Mode C.