Narrative:

Approximately 30 mi northwest of yak proceeding direct fai at 35000 ft we received a TCASII advisory for traffic at our 11-12 O'clock position and 15-20 mi (HSI's were in 320 NM scale). Looking directly upsun we could not identify any traffic in that location, and before we could call center, we received a TCASII RA to descend. Traffic was a B757 opposite direction aircraft at FL350. When clear of conflict we resumed our cruise at 35000 ft. Both aircraft Y and us inquired about the situation and requested a number to call. On arrival in fai, I called the center supervisor and discussed the situation. It appears that both aircraft were at the proper altitude, and the controller missed the conflict. There is a small sector of airspace in that area where both rvsm and cvsm rules and altitudes apply. Center notified that appropriate reports would be filed, event being evaluated at the center. There is no known information that I am aware of for the pilot group to know that this hazardous situation exists. If true, would recommend information released to pilots on size and location of mixed airspace rules.

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Original NASA ASRS Text

Title: FLT CREW OF B734 EXPERIENCED RA WITH OPPOSITE DIRECTION TFC AT FL350 IN ZAN RVSM TRANSITION AIRSPACE. BOTH ACFT ASSIGNED FL350.

Narrative: APPROX 30 MI NW OF YAK PROCEEDING DIRECT FAI AT 35000 FT WE RECEIVED A TCASII ADVISORY FOR TFC AT OUR 11-12 O'CLOCK POS AND 15-20 MI (HSI'S WERE IN 320 NM SCALE). LOOKING DIRECTLY UPSUN WE COULD NOT IDENT ANY TFC IN THAT LOCATION, AND BEFORE WE COULD CALL CTR, WE RECEIVED A TCASII RA TO DSND. TFC WAS A B757 OPPOSITE DIRECTION ACFT AT FL350. WHEN CLR OF CONFLICT WE RESUMED OUR CRUISE AT 35000 FT. BOTH ACFT Y AND US INQUIRED ABOUT THE SIT AND REQUESTED A NUMBER TO CALL. ON ARR IN FAI, I CALLED THE CTR SUPVR AND DISCUSSED THE SIT. IT APPEARS THAT BOTH ACFT WERE AT THE PROPER ALT, AND THE CTLR MISSED THE CONFLICT. THERE IS A SMALL SECTOR OF AIRSPACE IN THAT AREA WHERE BOTH RVSM AND CVSM RULES AND ALTS APPLY. CTR NOTIFIED THAT APPROPRIATE RPTS WOULD BE FILED, EVENT BEING EVALUATED AT THE CTR. THERE IS NO KNOWN INFO THAT I AM AWARE OF FOR THE PLT GROUP TO KNOW THAT THIS HAZARDOUS SIT EXISTS. IF TRUE, WOULD RECOMMEND INFO RELEASED TO PLTS ON SIZE AND LOCATION OF MIXED AIRSPACE RULES.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.