Narrative:

2 aircraft for lga were eastbound over etg at FL350. X1 was northbound over psb at FL320. ZNY called and the fll d-side released lower on the lga aircraft. I did not hear the coordination to know if X1 was referenced. I observed the front lga aircraft descend to FL320 while X2 remained at FL330. Since I thought that psb and mip were combined and X1 was over psb; I thought the ZNY controller was waiting for the aircraft to pass before descending X2. When I observed a descent on X2 I immediately turned X1 30 degrees left to increase lateral separation. Supplemental information from acn 786586: 2 aircraft eastbound to lga from ZOB to ZNY. 1 aircraft nwbound to yyz from ZNY to ZOB. New york called for controled descent on both lga aircraft. ZOB was never advised ZNY had split sectors milton and philipsburg; therefore; ZOB had valid reason to believe the yyz aircraft was known traffic for the lga aircraft; and control was released. It is very unusual for these 2 sectors to be decombined at XA50; and more unusual to not be informed of adjacent sector status when changes are made.

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Original NASA ASRS Text

Title: ZOB CTLR EXPERIENCED OPERROR AT APPROX FL320 WHEN ZOB/ZNY INTERFAC COORD FAILED RESULTING IN INCORRECT AIRSPACE/PROC ASSUMPTIONS.

Narrative: 2 ACFT FOR LGA WERE EBOUND OVER ETG AT FL350. X1 WAS NBOUND OVER PSB AT FL320. ZNY CALLED AND THE FLL D-SIDE RELEASED LOWER ON THE LGA ACFT. I DID NOT HEAR THE COORD TO KNOW IF X1 WAS REFED. I OBSERVED THE FRONT LGA ACFT DSND TO FL320 WHILE X2 REMAINED AT FL330. SINCE I THOUGHT THAT PSB AND MIP WERE COMBINED AND X1 WAS OVER PSB; I THOUGHT THE ZNY CTLR WAS WAITING FOR THE ACFT TO PASS BEFORE DSNDING X2. WHEN I OBSERVED A DSCNT ON X2 I IMMEDIATELY TURNED X1 30 DEGS L TO INCREASE LATERAL SEPARATION. SUPPLEMENTAL INFO FROM ACN 786586: 2 ACFT EBOUND TO LGA FROM ZOB TO ZNY. 1 ACFT NWBOUND TO YYZ FROM ZNY TO ZOB. NEW YORK CALLED FOR CTLED DSCNT ON BOTH LGA ACFT. ZOB WAS NEVER ADVISED ZNY HAD SPLIT SECTORS MILTON AND PHILIPSBURG; THEREFORE; ZOB HAD VALID REASON TO BELIEVE THE YYZ ACFT WAS KNOWN TFC FOR THE LGA ACFT; AND CTL WAS RELEASED. IT IS VERY UNUSUAL FOR THESE 2 SECTORS TO BE DECOMBINED AT XA50; AND MORE UNUSUAL TO NOT BE INFORMED OF ADJACENT SECTOR STATUS WHEN CHANGES ARE MADE.

Data retrieved from NASA's ASRS site as of May 2009 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.