Narrative:

Aircraft abcde was northeast bound landing ZZZ. He had been temporarily stopped at FL370. I needed to get him down to FL350 per LOA and was anticipating him possibly asking for lower. Aircraft afgde was southwest bound at FL400. I had not noticed that he was landing soon and was not anticipating him asking for lower. I was busy answering the green light when aircraft afgde requested lower and I did not hear him. I asked him to say again and aircraft afgde asked for lower. I was looking at aircraft abcde's data block and had in my head that it was him that asking for lower. I said aircraft afgde's call sign when I told him to descend and maintain FL350; but I still had in my head that I was talking to aircraft abcde and typed the altitude into his data block. A few seconds later I realized that aircraft afgde was descending head on with aircraft abcde. I asked aircraft afgde to verify assigned altitude thinking it might have been a bad mode C hit. Then I immediately stopped his descent at FL380. He later said he shot through 100 ft. I then descended aircraft abcde from FL370 to FL350. I asked aircraft abcde if he had received an RA and he said yes that he showed aircraft afgde 700 ft above him. I believe similar sounding call signs had something to do with situation. I also believe that as an flm; we are not as proficient as we should be to work a sector. We are only required to get 8 hours per month time on position. That is not enough time to be safe! Flm's should have to get more time on position to be safe or should not work sectors at all.

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Original NASA ASRS Text

Title: When an ARTCC Front Line Manager working a sector confused two similar call signs; a clearance was issued to the wrong aircraft resulting in a loss of separation. The reporter cited heavy traffic and lack of proficiency as contributory.

Narrative: Aircraft ABCDE was northeast bound landing ZZZ. He had been temporarily stopped at FL370. I needed to get him down to FL350 per LOA and was anticipating him possibly asking for lower. Aircraft AFGDE was southwest bound at FL400. I had not noticed that he was landing soon and was not anticipating him asking for lower. I was busy answering the green light when aircraft AFGDE requested lower and I did not hear him. I asked him to say again and aircraft AFGDE asked for lower. I was looking at aircraft ABCDE's data block and had in my head that it was him that asking for lower. I said aircraft AFGDE's call sign when I told him to descend and maintain FL350; but I still had in my head that I was talking to aircraft ABCDE and typed the altitude into his data block. A few seconds later I realized that aircraft AFGDE was descending head on with aircraft ABCDE. I asked aircraft AFGDE to verify assigned altitude thinking it might have been a bad mode C hit. Then I immediately stopped his descent at FL380. He later said he shot through 100 FT. I then descended aircraft ABCDE from FL370 to FL350. I asked aircraft ABCDE if he had received an RA and he said yes that he showed aircraft AFGDE 700 FT above him. I believe similar sounding call signs had something to do with situation. I also believe that as an FLM; we are not as proficient as we should be to work a sector. We are only required to get 8 hours per month time on position. That is not enough time to be safe! FLM's should have to get more time on position to be safe or should not work sectors at all.

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.