Narrative:

I will start with the cause, that being similar sounding call signs. I know acrs are pressed due to the number of flts operating in any given day: scheduled, chartered, ferry, etc. Whether the first officer working the ATC radio actually heard and answered a wrong call sign (which I do not think was the case), or the ATC controller misheard the readback, similar aircraft call signs between air carrier X aircraft, air carrier Y aircraft (and other major carriers) is a constant problem. We inadvertently vacated our assigned altitude for another assigned altitude but I had a 'bad' feeling that something was not right. Approaching from the southeast and landing to the south (runway 21L in dtw) generally requires you to maintain 12000 ft or sometimes 11000 ft MSL until abeam the dxo VOR/dtw airport. Why did the controllers clear us down to 3000 ft MSL 25 mi southeast of the airport? I had started 'down' as you would normally, when assigned a new altitude. Then that 'bad' feeling hit. I knew something was not right. Being familiar with the detroit procedures, I immediately queried the controller. 'Descend and maintain 11000 ft MSL,' he said. I promptly complied. No traffic conflict ever occurred and the flight uneventfully continued. We, of course, were at the time busy with descent and approach checks, 'briefing' for the approach in use, as well as discussing the need/termination of wing and engine anti-ice. I know how busy the ATC controller was, judging by the frequency congestion! Readbacks are important -- we all must listen and slow down our verbiage. I obviously would never climb or descend without clearance. Maybe our call signs need to be suffixed with a letter, ie, air carrier-Z abc.

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Original NASA ASRS Text

Title: CAPT OF AN ACR MLG STOPPED DSCNT AND QUESTIONED THE APCH CTLR AFTER SUSPECTING A RESPONSE TO ANOTHER ACFT SIMILAR SOUNDING CALL SIGN. CTLR THEN CLRED THE CAPT'S ACFT TO A LOWER ALT.

Narrative: I WILL START WITH THE CAUSE, THAT BEING SIMILAR SOUNDING CALL SIGNS. I KNOW ACRS ARE PRESSED DUE TO THE NUMBER OF FLTS OPERATING IN ANY GIVEN DAY: SCHEDULED, CHARTERED, FERRY, ETC. WHETHER THE FO WORKING THE ATC RADIO ACTUALLY HEARD AND ANSWERED A WRONG CALL SIGN (WHICH I DO NOT THINK WAS THE CASE), OR THE ATC CTLR MISHEARD THE READBACK, SIMILAR ACFT CALL SIGNS BTWN ACR X ACFT, ACR Y ACFT (AND OTHER MAJOR CARRIERS) IS A CONSTANT PROB. WE INADVERTENTLY VACATED OUR ASSIGNED ALT FOR ANOTHER ASSIGNED ALT BUT I HAD A 'BAD' FEELING THAT SOMETHING WAS NOT RIGHT. APCHING FROM THE SE AND LNDG TO THE S (RWY 21L IN DTW) GENERALLY REQUIRES YOU TO MAINTAIN 12000 FT OR SOMETIMES 11000 FT MSL UNTIL ABEAM THE DXO VOR/DTW ARPT. WHY DID THE CTLRS CLR US DOWN TO 3000 FT MSL 25 MI SE OF THE ARPT? I HAD STARTED 'DOWN' AS YOU WOULD NORMALLY, WHEN ASSIGNED A NEW ALT. THEN THAT 'BAD' FEELING HIT. I KNEW SOMETHING WAS NOT RIGHT. BEING FAMILIAR WITH THE DETROIT PROCS, I IMMEDIATELY QUERIED THE CTLR. 'DSND AND MAINTAIN 11000 FT MSL,' HE SAID. I PROMPTLY COMPLIED. NO TFC CONFLICT EVER OCCURRED AND THE FLT UNEVENTFULLY CONTINUED. WE, OF COURSE, WERE AT THE TIME BUSY WITH DSCNT AND APCH CHKS, 'BRIEFING' FOR THE APCH IN USE, AS WELL AS DISCUSSING THE NEED/TERMINATION OF WING AND ENG ANTI-ICE. I KNOW HOW BUSY THE ATC CTLR WAS, JUDGING BY THE FREQ CONGESTION! READBACKS ARE IMPORTANT -- WE ALL MUST LISTEN AND SLOW DOWN OUR VERBIAGE. I OBVIOUSLY WOULD NEVER CLB OR DSND WITHOUT CLRNC. MAYBE OUR CALL SIGNS NEED TO BE SUFFIXED WITH A LETTER, IE, ACR-Z ABC.

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.