Air carrier flight crew acknowledged ARTCC controller clearance for descent that was for another air carrier, with similar sounding call sign. Apparently, ATC did not hear both air carrier's acknowledgment. Aircraft returned to assigned altitude and proceeded to destination without further incident.

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Attributes
ACN	390133
Time
Date	199712
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mgm
State Reference	AL
Altitude	msl bound lower : 34300 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 13000
ASRS Report	390133
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 12000 flight time type : 200
ASRS Report	390140
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X and air carrier Y were on same frequency. Confusion occurred over clearance from FL350 to FL240. We read back clearance and started descent when we were told it was for air carrier Y. Like- sounding call signs and controller not listening to readback allowed problem to occur. Supplemental information from acn 390140: descent to FL240 was given and acknowledged by captain -- no reply from ATC. At 34300 ft ATC told us to return to 35000 ft and that the clearance was for another aircraft. Apparently we both acknowledged the descent clearance and blocked each other out. When ATC didn't reply we assumed the clearance was given, we acknowledged and that was that. I began the descent.

Original NASA ASRS Text

Title: ACR FLC ACKNOWLEDGED ARTCC CTLR CLRNC FOR DSCNT THAT WAS FOR ANOTHER ACR, WITH SIMILAR SOUNDING CALL SIGN. APPARENTLY, ATC DID NOT HEAR BOTH ACR'S ACKNOWLEDGMENT. ACFT RETURNED TO ASSIGNED ALT AND PROCEEDED TO DEST WITHOUT FURTHER INCIDENT.

Narrative: ACR X AND ACR Y WERE ON SAME FREQ. CONFUSION OCCURRED OVER CLRNC FROM FL350 TO FL240. WE READ BACK CLRNC AND STARTED DSCNT WHEN WE WERE TOLD IT WAS FOR ACR Y. LIKE- SOUNDING CALL SIGNS AND CTLR NOT LISTENING TO READBACK ALLOWED PROB TO OCCUR. SUPPLEMENTAL INFO FROM ACN 390140: DSCNT TO FL240 WAS GIVEN AND ACKNOWLEDGED BY CAPT -- NO REPLY FROM ATC. AT 34300 FT ATC TOLD US TO RETURN TO 35000 FT AND THAT THE CLRNC WAS FOR ANOTHER ACFT. APPARENTLY WE BOTH ACKNOWLEDGED THE DSCNT CLRNC AND BLOCKED EACH OTHER OUT. WHEN ATC DIDN'T REPLY WE ASSUMED THE CLRNC WAS GIVEN, WE ACKNOWLEDGED AND THAT WAS THAT. I BEGAN THE DSCNT.

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.