Narrative:

We had just checked in with ZID. We reported 'level FL290.' the controller responded 'roger, flight X, descend and maintain FL260.' I responded 'flight X vacating FL290 for FL260.' the captain initiated a descent with the autoplt. At FL285, center asked us what our altitude was. I responded that we were descending to FL260. The controller told us flight Z was 'X mi and 1000 ft below.' I asked what altitude he wanted us at. He responded with the question of who issued the descent. The autoplt was disengaged, and a climb was started. About this time, the TCASII issued a TA. I again asked what altitude he needed us at. He responded FL290, and to report reaching. After which, no further questions were asked and the flight continued normally. Moments later, flight Y (we were flight X) was told to descend and maintain FL260. Factors contributing: center congestion (he was busy). Similar call sign. Controller confusion delaying resolution command(south). Controller should have, upon noticing the potential conflict, issued a command to resolve the situation in lieu of questioning our actions. I believe the controller issued us the descent by confusing us with another company on frequency. The captain concurred that we were issued the descent. If I had made the mistake, my response was not understood by the controller as a potential/actual mistake. Since we had 1000 ft separation within 5 mi, I believe no action will be taken against controller/crew. Supplemental information from acn 539827: N733 wbound and controled by ZID 89 at FL280. E145 eastbound and controled by ZID 88 at FL290. ZID 88 issued a clearance to the E145 to descend to FL240. This clearance meant for a company aircraft with a similar call sign. The controller transposed numbers. The E145 began to descend. The B733 was at FL280, opposite direction and converging. With aircraft 10 mi apart, B7334 reported an RA and descended. I noticed the 3145 descending just as conflict alert went off and the RA was reported. I affirmed the traffic to the B733. ZID 88 cleared the E145 back to FL290. I gave the B733 approval to maneuver as needed. Vertical separation was not lost. B733 descended to FL270. E145 descended to FL283 and then climbed back to FL290.

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Original NASA ASRS Text

Title: OPDEV SET UP A POTENTIAL CONFLICT BTWN OPPOSITE DIRECTION TFC DURING AN ERRED DSCNT CLRNC ISSUED BY ARTCC RADAR CTLR IN A TRANSPOSITION OF SIMILAR SOUNDING CALL SIGNS WITH 2 ACFT 50 NM E OF VHP, IN.

Narrative: WE HAD JUST CHKED IN WITH ZID. WE RPTED 'LEVEL FL290.' THE CTLR RESPONDED 'ROGER, FLT X, DSND AND MAINTAIN FL260.' I RESPONDED 'FLT X VACATING FL290 FOR FL260.' THE CAPT INITIATED A DSCNT WITH THE AUTOPLT. AT FL285, CTR ASKED US WHAT OUR ALT WAS. I RESPONDED THAT WE WERE DSNDING TO FL260. THE CTLR TOLD US FLT Z WAS 'X MI AND 1000 FT BELOW.' I ASKED WHAT ALT HE WANTED US AT. HE RESPONDED WITH THE QUESTION OF WHO ISSUED THE DSCNT. THE AUTOPLT WAS DISENGAGED, AND A CLB WAS STARTED. ABOUT THIS TIME, THE TCASII ISSUED A TA. I AGAIN ASKED WHAT ALT HE NEEDED US AT. HE RESPONDED FL290, AND TO RPT REACHING. AFTER WHICH, NO FURTHER QUESTIONS WERE ASKED AND THE FLT CONTINUED NORMALLY. MOMENTS LATER, FLT Y (WE WERE FLT X) WAS TOLD TO DSND AND MAINTAIN FL260. FACTORS CONTRIBUTING: CTR CONGESTION (HE WAS BUSY). SIMILAR CALL SIGN. CTLR CONFUSION DELAYING RESOLUTION COMMAND(S). CTLR SHOULD HAVE, UPON NOTICING THE POTENTIAL CONFLICT, ISSUED A COMMAND TO RESOLVE THE SIT IN LIEU OF QUESTIONING OUR ACTIONS. I BELIEVE THE CTLR ISSUED US THE DSCNT BY CONFUSING US WITH ANOTHER COMPANY ON FREQ. THE CAPT CONCURRED THAT WE WERE ISSUED THE DSCNT. IF I HAD MADE THE MISTAKE, MY RESPONSE WAS NOT UNDERSTOOD BY THE CTLR AS A POTENTIAL/ACTUAL MISTAKE. SINCE WE HAD 1000 FT SEPARATION WITHIN 5 MI, I BELIEVE NO ACTION WILL BE TAKEN AGAINST CTLR/CREW. SUPPLEMENTAL INFO FROM ACN 539827: N733 WBOUND AND CTLED BY ZID 89 AT FL280. E145 EBOUND AND CTLED BY ZID 88 AT FL290. ZID 88 ISSUED A CLRNC TO THE E145 TO DSND TO FL240. THIS CLRNC MEANT FOR A COMPANY ACFT WITH A SIMILAR CALL SIGN. THE CTLR TRANSPOSED NUMBERS. THE E145 BEGAN TO DSND. THE B733 WAS AT FL280, OPPOSITE DIRECTION AND CONVERGING. WITH ACFT 10 MI APART, B7334 RPTED AN RA AND DSNDED. I NOTICED THE 3145 DSNDING JUST AS CONFLICT ALERT WENT OFF AND THE RA WAS RPTED. I AFFIRMED THE TFC TO THE B733. ZID 88 CLRED THE E145 BACK TO FL290. I GAVE THE B733 APPROVAL TO MANEUVER AS NEEDED. VERT SEPARATION WAS NOT LOST. B733 DSNDED TO FL270. E145 DSNDED TO FL283 AND THEN CLBED BACK TO FL290.

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.