Narrative:

Our large transport was cleared to FL390. We broke out on top at about FL310. At about FL340 we spotted converging traffic at 11 O'clock high. I asked center the altitude of the traffic. The center's reply was, 'level off at 350.' we were already through FL346. A smooth level off took us up to FL352 and then back down to FL350. As we watched another air carrier widebody transport pass directly over us, center confirmed his altitude as FL370. Had we been IMC, I feel a midair was an 80-90% probability.

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Original NASA ASRS Text

Title: OPERATIONAL ERROR OF ALLOWING ACR FLT TO ALMOST CLIMB THROUGH OCCUPIED ALT OF ANOTHER ACFT FLT CREATES LOSS OF SEPARATION WITH THE POTENTIAL OF A NMAC OR ACTUAL MIDAIR COLLISION.

Narrative: OUR LGT WAS CLRED TO FL390. WE BROKE OUT ON TOP AT ABOUT FL310. AT ABOUT FL340 WE SPOTTED CONVERGING TFC AT 11 O'CLOCK HIGH. I ASKED CENTER THE ALT OF THE TFC. THE CENTER'S REPLY WAS, 'LEVEL OFF AT 350.' WE WERE ALREADY THROUGH FL346. A SMOOTH LEVEL OFF TOOK US UP TO FL352 AND THEN BACK DOWN TO FL350. AS WE WATCHED ANOTHER ACR WDB PASS DIRECTLY OVER US, CENTER CONFIRMED HIS ALT AS FL370. HAD WE BEEN IMC, I FEEL A MIDAIR WAS AN 80-90% PROBABILITY.

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.