B737-800
Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction
ATC Issue All Types; Conflict Airborne Conflict
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew Executed Go Around / Missed Approach
Airport; Environment - Non Weather Related; Procedure; Human Factors
I am writing this report to identify an unsafe trend during night visual approaches.  During an ILS approach to 31R at JFK upon check in with tower we were told our traffic was a B-747 5 miles in front of us; 4 miles from the airport.  Tower asked us if we had the traffic in sight.  There was a right to left crosswind and several blinking lights between us and the runway.  We could not confirm which airplane was our sequence and since it was night; we could not identify a Boeing 747.  I said to the pilot monitoring (PM) 'I don't have the traffic' and he radioed [the] tower.  They said continue.  Three miles later on glideslope and passing 2000' approaching ZULAB; tower reported 'traffic one mile out on final report traffic in sight.'  Again; there were several flashing lights on or near the airport and while this traffic was going to be no factor; I again told the PM that I could not identify the traffic as our sequence.  He radioed the tower not in sight; asked about our spacing and requested to continue the ILS.  Tower commanded us to level off at 2000' and maintain runway heading.  I executed a TOGA to an immediate level off at 2000'; flew runway heading and waited for instructions.  The next tower instruction was 'Traffic on Runway; can you conduct a visual approach from your current position?'  The answer was no as we had proceeded well above a 3 degree glide slope.  Tower gave us instructions to turn and change freq to approach control where we were vectored to an uneventful approach and landing.   ATC tower controllers are using visual identification during night hours way to often and in crowded airspace.  There is no possible way to identify an aircraft at night unless there are no other flashing lights in the sector you are looking.  In the absence of positive identification; it is erroneous to guess at where the traffic should be based on the controller's direction.  Several years ago an airplane following us into EWR mistakenly identified our sequence; [another airline] airplane.  They flew within 2 miles of us thinking they should be following our sequence on final.  The issue then and now; is how do you identify one blinking light from another?  In our case we did the right thing and said we could not positively identify traffic.  Unfortunately; for some reason; JFK tower didn't feel 5 miles separation on an ILS was enough and they sent us around.  I certainly hope this was not punitive for not calling out traffic; but I have landed in IFR weather with less separation before.
A B737-800 pilot expressed his concern that JFK ATC is utilizing uncertain identifications of sequenced traffic at night to permit visual approach clearances by aircraft unable to positively identify one another.