Narrative:

It was actually on the return flight to phl with the same flight number of X012; but the program did not have that as an option to select. While enroute we were talking to ZNY center and we heard abcd X021 was also on frequency. The captain and I made note of it to each other as to how it could get confusing so that we would be on the listen. ATC did not mention to either of us that the other similar call sign was on frequency. We were given our clearance as usual to cross cofax at FL250. The captain set the altitude preselect. I confirmed it and then began an appropriate descent. Sometime during the descent ATC gave the following clearance; 'abcd X021 descend and maintain FL260.' the other aircraft appropriately responded with their call sign and the read back of the clearance to descend to FL260. There was no confusion in either the ATC clearance or the read back. Since I was on the lookout for the similar call sign; I verified with the captain that he too heard abcd X021. He agreed that both parties had used X021. After we had descended to 25;700; the controller asked abcd X021 to state their assigned altitude. They read back FL260. The controller stated that that descent was not for them (this was several minutes later since the read back.) my captain then asked if FL260 had been for us and we were told it was. He then cleared us to FL250 as we were still in the descent. We were very shortly thereafter given a frequency change and there was no further incident. So while we did in fact have an altitude deviation based on what the controller had intended there was no deviation based on what either us or abcd X021 was actually cleared to do. I am only filing this since it is definitely a safety concern since we have all had similar issues. Plus; in case the other aircraft files a report; I am hoping this can be linked to their report as further information. This could have been prevented a few ways. 1) the controller could have warned us both upfront that there were the other respective similar sounding call sign on frequency. Just because my captain and I had been listening carefully since we recognized the similar call sign; doesn't mean that the other crew knew we were also on frequency. There are plenty of instances on an almost daily basis when controllers issue the wrong call sign even when there is no other one similar on frequency. When we query them; or don't respond to the wrong call sign; they get mad at us as if we heard it wrong. That makes us less likely to query them and more likely for us to think that it is simply another aircraft on frequency. 2) we could have queried the controller every time he used either call sign just to make sure that he was in fact using the right one for the right aircraft. (Which he was not this one time) and would have led to a lot of extra radio chatter. 3) the controller could have used phraseology that many other controllers use like; 'abcd X012; stop your descent at FL260.' that would have been much clearer since the other aircraft was previously level and had not been given a descent clearance and we were already in a descent. By using the phrase descend and maintain and have it being a higher altitude than we were already cleared; it made more sense to be the other aircraft's clearance. Recently; I had a similar event that was not worth reporting where we were in a climb around FL230 and assigned FL310. A few minutes later we received the clearance; 'abcd XXXX climb and maintain FL290.' the captain responded by stating that we were previously cleared to FL310. The controller snapped like we were stupid with a remark like; yea; now I'm stopping you at FL290. That would have been handled much better had he just stated 'abcd XXXX; stop your climb at FL290.' 4) the controller could have actually listened to their read back of the clearance in which they stated abcd X021. Had he heard that and not meant to issue the clearance to that call sign; he could have caught itat that point and it never would have been an issue.

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Original NASA ASRS Text

Title: ZNY ATC with similar call sign aircraft on frequency inadvertently issued a descent clearance to the incorrect aircraft.

Narrative: It was actually on the return flight to PHL with the same flight number of X012; but the program did not have that as an option to select. While enroute we were talking to ZNY Center and we heard ABCD X021 was also on frequency. The Captain and I made note of it to each other as to how it could get confusing so that we would be on the listen. ATC did not mention to either of us that the other similar call sign was on frequency. We were given our clearance as usual to cross COFAX at FL250. The Captain set the altitude preselect. I confirmed it and then began an appropriate descent. Sometime during the descent ATC gave the following clearance; 'ABCD X021 descend and maintain FL260.' The other aircraft appropriately responded with their call sign and the read back of the clearance to descend to FL260. There was no confusion in either the ATC clearance or the read back. Since I was on the lookout for the similar call sign; I verified with the Captain that he too heard ABCD X021. He agreed that both parties had used X021. After we had descended to 25;700; the Controller asked ABCD X021 to state their assigned altitude. They read back FL260. The Controller stated that that descent was not for them (this was several minutes later since the read back.) My Captain then asked if FL260 had been for us and we were told it was. He then cleared us to FL250 as we were still in the descent. We were very shortly thereafter given a frequency change and there was no further incident. So while we did in fact have an altitude deviation based on what the Controller had intended there was no deviation based on what either us or ABCD X021 was ACTUALLY cleared to do. I am only filing this since it is definitely a safety concern since we have all had similar issues. Plus; in case the other aircraft files a report; I am hoping this can be linked to their report as further information. This could have been prevented a few ways. 1) The Controller could have warned us both upfront that there were the other respective similar sounding call sign on frequency. Just because my Captain and I had been listening carefully since we recognized the similar call sign; doesn't mean that the other crew knew we were also on frequency. There are plenty of instances on an almost daily basis when Controllers issue the wrong call sign even when there is no other one similar on frequency. When we query them; or don't respond to the WRONG call sign; they get mad at us as if we heard it wrong. That makes us less likely to query them and more likely for us to think that it is simply another aircraft on frequency. 2) We could have queried the Controller EVERY time he used either call sign just to make sure that he was in fact using the right one for the right aircraft. (Which he was not this one time) and would have led to a lot of extra radio chatter. 3) The Controller could have used phraseology that many other controllers use like; 'ABCD X012; stop your descent at FL260.' That would have been much clearer since the other aircraft was previously level and had not been given a descent clearance and we were already in a descent. By using the phrase descend and maintain and have it being a higher altitude than we were already cleared; it made more sense to be the other aircraft's clearance. Recently; I had a similar event that was not worth reporting where we were in a climb around FL230 and assigned FL310. A few minutes later we received the clearance; 'ABCD XXXX climb and maintain FL290.' The Captain responded by stating that we were previously cleared to FL310. The Controller snapped like we were stupid with a remark like; yea; now I'm stopping you at FL290. That would have been handled much better had he just stated 'ABCD XXXX; stop your climb at FL290.' 4) The Controller could have actually listened to their read back of the clearance in which they stated ABCD X021. Had he heard that and not meant to issue the clearance to that call sign; he could have caught itat that point and it never would have been an issue.

Data retrieved from NASA's ASRS site as of April 2012 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.