Narrative:

At the time of the error, I had 2 aircraft on frequency with very similar call signs. (Fgt xx and fgt axx). Fgt xx was sebnd at 12000 with a request for FL210. He was stopped at 12000 for traffic northbound at 13000, small transport Z. Fgt axx was at FL200 requesting FL220. After fgt axx had cleared a military refueling track I climbed him to FL220. After listening to the tape it was learned that I had transposed the call signs and actually issued a climb clearance to fgt xx resulting in loss of sep with small transport Z.

Google
 

Original NASA ASRS Text

Title: ARTCC RADAR CTLR TRANSPOSED CALL SIGNS ON FGT ACFT AND CLEARED WRONG ONE TO CLIMB CAUSING LESS THAN STANDARD SEPARATION WITH AN SMT.

Narrative: AT THE TIME OF THE ERROR, I HAD 2 ACFT ON FREQ WITH VERY SIMILAR CALL SIGNS. (FGT XX AND FGT AXX). FGT XX WAS SEBND AT 12000 WITH A REQUEST FOR FL210. HE WAS STOPPED AT 12000 FOR TFC NBOUND AT 13000, SMT Z. FGT AXX WAS AT FL200 REQUESTING FL220. AFTER FGT AXX HAD CLRED A MIL REFUELING TRACK I CLBED HIM TO FL220. AFTER LISTENING TO THE TAPE IT WAS LEARNED THAT I HAD TRANSPOSED THE CALL SIGNS AND ACTUALLY ISSUED A CLB CLRNC TO FGT XX RESULTING IN LOSS OF SEP WITH SMT Z.

Data retrieved from NASA's ASRS site as of August 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.