Narrative:

We had been in cruise flight for approximately 10 minutes and were about to enter an area of reported moderate 'plus' turbulence. The captain went off frequency to advise the flight attendants to be seated. As soon as I took over the radios; I heard ATC give an aircraft with a similar call sign an instruction to descend to 24;000 feet. I thought it was us; so I read back the instruction to ATC and waited for a moment to ensure I was not corrected by ATC. I then started a descent. About 1;600 feet into the descent; ATC queried us why we were lower than expected. At this time the captain came back up on the comms and stated something to the effect we were cleared down to 24;000 feet. ATC said they never gave that clearance; so we immediately initiated a climb back to 28;000 feet. There was no RA or traffic conflict. ATC made no further mention of the event.the left earphone on my headset had failed shortly after blocking out; so that reduced some of my ability to clearly hear ATC transmissions. Secondly; I was flying single pilot and laced the redundancy of a second pilot to back me up at the moment. Also; there was an aircraft with a similar sounding call sign on frequency. Finally; ATC did not correct my mistaken pickup of a descent clearance when I read back the clearance. I should have been more situationally aware that our position was too far out from our destination for such a descent clearance to be given to us. Thus; I should have verified (what I thought was) a descent clearance for us with ATC before. Also; I should have turned the volume up on my headset more than I did.

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Original NASA ASRS Text

Title: CRJ-200 First Officer reported following a clearance for another aircraft with a similar callsign; resulting in an altitude deviation.

Narrative: We had been in cruise flight for approximately 10 minutes and were about to enter an area of reported moderate 'plus' turbulence. The Captain went off frequency to advise the flight attendants to be seated. As soon as I took over the radios; I heard ATC give an aircraft with a similar call sign an instruction to descend to 24;000 feet. I thought it was us; so I read back the instruction to ATC and waited for a moment to ensure I was not corrected by ATC. I then started a descent. About 1;600 feet into the descent; ATC queried us why we were lower than expected. At this time the Captain came back up on the comms and stated something to the effect we were cleared down to 24;000 feet. ATC said they never gave that clearance; so we immediately initiated a climb back to 28;000 feet. There was no RA or traffic conflict. ATC made no further mention of the event.The left earphone on my headset had failed shortly after blocking out; so that reduced some of my ability to clearly hear ATC transmissions. Secondly; I was flying single pilot and laced the redundancy of a second pilot to back me up at the moment. Also; there was an aircraft with a similar sounding call sign on frequency. Finally; ATC did not correct my mistaken pickup of a descent clearance when I read back the clearance. I should have been more situationally aware that our position was too far out from our destination for such a descent clearance to be given to us. Thus; I should have verified (what I thought was) a descent clearance for us with ATC before. Also; I should have turned the volume up on my headset more than I did.

Data retrieved from NASA's ASRS site 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.