Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2
Communication Breakdown; Confusion; Situational Awareness; Fatigue
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors; Procedure; Staffing
I had two Air Carrier X aircraft inbound each going to a different runway. Aircraft X and Aircraft Y. I was busy and instructed the wrong Aircraft to slow to 250 knots then descend to 7;000 feet. I descended the top aircraft rather than the bottom aircraft. I saw Aircraft X slowing from 300 to 250 knots instead of the bottom aircraft. I thought something was wrong and instructed the aircraft to maintain 11;000 feet. They had already started down and got as low as 10;700 feet. Aircraft Y had the other aircraft in sight however a LOSS had already occurred. Similar sounding call signs and an above average traffic volume lead me to instruct the wrong airplane to start a descent with another aircraft beneath them. Long term fatigue from 6 day weeks and a quick turn definitely contributed to this mistake. The last few weeks have been full of short breaks; high position time; and lots of convective activity.
C90 TRACON Controller reported an airborne conflict after descending the wrong aircraft due to similar sounding callsign confusion.