Narrative:

Approach control issued a heading and altitude clearance to an air carrier B aircraft. We thought the clearance was for us and read back clearance to ATC. While descending to 4000 ft (the air carrier B clearance) we heard air carrier B advise ATC that an air carrier a aircraft had read back what he thought was his clearance. We stopped descending at 7500 ft MSL, called ATC and asked for a confirmation of our assigned altitude and heading. ATC confirmed what air carrier B had pointed out, we did indeed take his clearance and ATC accepted our readback of air carrier B's clearance without any comment. Frequency was not congested at time -- certainly ATC heard the wrong aircraft respond or the squeal of 2 aircraft broadcasting at the same time, an indication, of readback/hearback error. Similar digits in both acfts' call signs.

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Original NASA ASRS Text

Title: MLG TOOK CLRNC MEANT FOR ANOTHER ACFT AND DSNDED OUT OF HIS ASSIGNED ALT.

Narrative: APCH CTL ISSUED A HDG AND ALT CLRNC TO AN ACR B ACFT. WE THOUGHT THE CLRNC WAS FOR US AND READ BACK CLRNC TO ATC. WHILE DSNDING TO 4000 FT (THE ACR B CLRNC) WE HEARD ACR B ADVISE ATC THAT AN ACR A ACFT HAD READ BACK WHAT HE THOUGHT WAS HIS CLRNC. WE STOPPED DSNDING AT 7500 FT MSL, CALLED ATC AND ASKED FOR A CONFIRMATION OF OUR ASSIGNED ALT AND HDG. ATC CONFIRMED WHAT ACR B HAD POINTED OUT, WE DID INDEED TAKE HIS CLRNC AND ATC ACCEPTED OUR READBACK OF ACR B'S CLRNC WITHOUT ANY COMMENT. FREQ WAS NOT CONGESTED AT TIME -- CERTAINLY ATC HEARD THE WRONG ACFT RESPOND OR THE SQUEAL OF 2 ACFT BROADCASTING AT THE SAME TIME, AN INDICATION, OF READBACK/HEARBACK ERROR. SIMILAR DIGITS IN BOTH ACFTS' CALL SIGNS.

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.