RPTR OBSERVES ON HIS TCASII ANOTHER ACR CLB THROUGH HIS ALT WITHOUT CLRNC.

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ON THE NIGHT OF FEB/TUE/96 I WAS FO ON AN ACR A FLT; A B767-300; FROM SAO PAULO; BRAZIL; TO JFK INTL; NY. WHILE IN CRUISE NBOUND IN A NON RADAR ENVIRONMENT; APPROX 100 NM S OF LONAS INTXN ON AIRWAY UA312; WE OBSERVED OVERTAKING TFC ON TCASII 40 MI BEHIND US AT FL280. THE TFC COMMENCED A SLOW CLB THROUGH OUR ALT TO FL370; WHERE IT REMAINED BRIEFLY BEFORE DSNDING TO FL280 WHERE IT PASSED US A SHORT WHILE LATER. ATTEMPTS TO CONTACT BELEM CTR ON VHF AND THE ACFT ON BLIND BROADCAST FREQ WERE UNSUCCESSFUL. LATER ON SUBSEQUENT CTR FREQS; WE DETERMINED THE ACFT TO BE AN ACR B FLT. THIS EVENT ILLUSTRATES AN INCREASING TREND IN SOUTH AMERICAN FLYING. CERTAIN UNPROFESSIONAL OPERATORS ROUTINELY CHANGE ALT IN A NON RADAR ENVIRONMENT WITHOUT ATC CLRNC TO AVOID WX OR TO CONSERVE FUEL. IN THIS CASE WX WAS NOT A FACTOR; BUT THE FLT WAS OVERHEARD ASKING FOR A HIGHER FLT LEVEL TO AVOID A FUEL STOP. IN THIS SIT; STANDARD SEPARATION WAS VIOLATED BY THE ACR B FLT. RECOMMENDATION: KEEP YOUR TCASII ON; YOUR EYES AND EARS OPEN.