Narrative:

We departed msp approximately 5 min behind a company flight that was running late. We were flight XY6 and they were XY4. In the chicago area we were about 5 mi behind flight XY4 when we heard approach control clear him to turn right to 180 degree (he was at 4000 ft, heading 090 degree, about 14 mi ene of ord VOR). At this time we were descending out of 7000 ft to 4000 ft heading 090 about 8 DME ene the ord VOR. I could see the company flight turning ahead of us and heard approach give a air carrier Y flight approach clearance to 27R. I could see this air carrier Y flight at our 1 O'clock position about 5 mi ahead. Then approach gave us (XY6) clearance to turn right to 180 degree heading. I thought 'he may have room to fit us in ahead of the air carrier Y' but it looked 'tight'. About this time I wondered if he) thought he had not given the 180 degree heading to XY4 and was saying it to him again when he used our call sign (XY6). 'Air carrier XY6 turn right to a heading of 180 degrees'. This is obviously what happened because as I was going to point out to him that it wasn't going to work he came back on the air with orders for an immediate tight right turn to 040. Followed by turns to 070 degrees, then 090 degrees. This put us back on an extended downwind for 27R again and no further unusual occurrences were noted. It is obvious to me that the similar call signs were the reason for the confusion. Supplemental information from acn 200990: after we were established ATC realized their error and instructed us to make a hard right turn to 040 degrees to avoid ILS 27L and 27R approach courses. ATC did not query us to our heading so I would assume they realized it was their error. We were VMC on top and saw no conflict with other traffic. Contributing factors: air carrier XY4 was 1 hour late leaving msp to ord and we departed immediately behind them from 11R in msp. We were aware of the similar call signs so we were extra cautious. Similar call signs combined with identical flight plans led to the ATC error.

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Original NASA ASRS Text

Title: SIMILAR SOUNDING CALL SIGNS BTWN 2 ACR'S ON APCH CAUSE CTLR TO ISSUE CLRNC TO WRONG ACFT. LTSS.

Narrative: WE DEPARTED MSP APPROX 5 MIN BEHIND A COMPANY FLT THAT WAS RUNNING LATE. WE WERE FLT XY6 AND THEY WERE XY4. IN THE CHICAGO AREA WE WERE ABOUT 5 MI BEHIND FLT XY4 WHEN WE HEARD APCH CTL CLR HIM TO TURN R TO 180 DEG (HE WAS AT 4000 FT, HDG 090 DEG, ABOUT 14 MI ENE OF ORD VOR). AT THIS TIME WE WERE DSNDING OUT OF 7000 FT TO 4000 FT HDG 090 ABOUT 8 DME ENE THE ORD VOR. I COULD SEE THE COMPANY FLT TURNING AHEAD OF US AND HEARD APCH GIVE A ACR Y FLT APCH CLRNC TO 27R. I COULD SEE THIS ACR Y FLT AT OUR 1 O'CLOCK POS ABOUT 5 MI AHEAD. THEN APCH GAVE US (XY6) CLRNC TO TURN R TO 180 DEG HDG. I THOUGHT 'HE MAY HAVE ROOM TO FIT US IN AHEAD OF THE ACR Y' BUT IT LOOKED 'TIGHT'. ABOUT THIS TIME I WONDERED IF HE) THOUGHT HE HAD NOT GIVEN THE 180 DEG HDG TO XY4 AND WAS SAYING IT TO HIM AGAIN WHEN HE USED OUR CALL SIGN (XY6). 'ACR XY6 TURN R TO A HDG OF 180 DEGS'. THIS IS OBVIOUSLY WHAT HAPPENED BECAUSE AS I WAS GOING TO POINT OUT TO HIM THAT IT WASN'T GOING TO WORK HE CAME BACK ON THE AIR WITH ORDERS FOR AN IMMEDIATE TIGHT R TURN TO 040. FOLLOWED BY TURNS TO 070 DEGS, THEN 090 DEGS. THIS PUT US BACK ON AN EXTENDED DOWNWIND FOR 27R AGAIN AND NO FURTHER UNUSUAL OCCURRENCES WERE NOTED. IT IS OBVIOUS TO ME THAT THE SIMILAR CALL SIGNS WERE THE REASON FOR THE CONFUSION. SUPPLEMENTAL INFO FROM ACN 200990: AFTER WE WERE ESTABLISHED ATC REALIZED THEIR ERROR AND INSTRUCTED US TO MAKE A HARD R TURN TO 040 DEGS TO AVOID ILS 27L AND 27R APCH COURSES. ATC DID NOT QUERY US TO OUR HDG SO I WOULD ASSUME THEY REALIZED IT WAS THEIR ERROR. WE WERE VMC ON TOP AND SAW NO CONFLICT WITH OTHER TFC. CONTRIBUTING FACTORS: ACR XY4 WAS 1 HR LATE LEAVING MSP TO ORD AND WE DEPARTED IMMEDIATELY BEHIND THEM FROM 11R IN MSP. WE WERE AWARE OF THE SIMILAR CALL SIGNS SO WE WERE EXTRA CAUTIOUS. SIMILAR CALL SIGNS COMBINED WITH IDENTICAL FLT PLANS LED TO THE ATC ERROR.

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.