POTENTIAL CONFLICT DURING AN OVERWATER OP FOREIGN AIRSPACE. OPERROR.

Narrative

DEPARTING NAGOYA; JAPAN; FOR AGANA; GUAM. TOKYO CTR ISSUED CLRNC TO 'CLB AND MAINTAIN FL330; AT NOGAK CLB TO FL370.' CLRNC WAS READ BACK TO CTR AND AGAIN DURING A SUBSEQUENT POS RPT (AT ADKAK PRIOR TO NOGAK INTXN) TO TOKYO RADIO. AT NOGAK A CLB WAS INITIATED FROM FL330 TO FL370. APPROX 12 NM S OF NOGAK AT 35200 FT AN ONBOARD TCASII TA WAS RECEIVED INDICATING TFC AT 12 O'CLOCK; 200 FT BELOW; OPPOSITE DIRECTION. CLB CONTINUED TO FL370. PASSING FL360 SUBJECT ACFT PASSED APPROX 1 NM W (OFF R WING); 1000 FT BELOW. NO EVASIVE ACTION WAS REQUIRED; NO TCASII RA WAS RECEIVED. COMMERCIAL RADIO WAS ADVISED AND AN ASR FILED. 10 YRS OF E ASIAN FLYING HAS SEEN CONSIDERABLE IMPROVEMENT IN THE SKILLS AND ABILITIES OF JAPANESE CTLRS. THE CONDITIONAL CLRNC ISSUED BY TOKYO CTR TO CLB TO FL370 AT NOGAK APPEARED TO BE A NONSTANDARD PROC; OR AT A MINIMUM A TYPE OF CLRNC INFREQUENTLY RECEIVED. THE CLRNC WAS VERIFIED TWICE; ONCE WITH TOKYO CTR AND LATER WITH TOKYO RADIO. IN ADDITION; ALL 3 FLT DECK CREW MEMBERS WERE IN AGREEMENT AS TO THE EXACT NATURE OF THE CLRNC (IE; THE CLRNC WAS NOT 'EXPECT FL370 AT NOGAK'). THE BIG SKY THEORY IN COMBINATION WITH ONBOARD TCASII PREVENTED A POTENTIAL NEAR MIDAIR EVENT. AIR CREW ACTIONS COULD HAVE INCLUDED A THIRD VERIFICATION OF THE CLRNC PRIOR TO DEPARTING FL330. HOWEVER; IT IS QUESTIONABLE IF THIS STEP WOULD HAVE PREVENTED THIS OCCURRENCE.