Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 6.0
Communication Breakdown; Confusion; Situational Awareness
ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Other / Unknown
Air Traffic Control Issued New Clearance; Flight Crew Landed in Emergency Condition; General Flight Cancelled / Delayed
I had track control of Aircraft X but the aircraft was still 20 miles outside of my airspace. I was also working Aircraft Y a departure who was in my airspace and climbing along the SID. Aircraft X said 'Center; Aircraft X'. I said 'go ahead' with no callsign. Aircraft X says 'we need to divert' with no callsign. I am looking at Aircraft Y the whole time and think that is who I am talking to. I cleared Aircraft Y 'via right hand turn to ZZZ...' and gave him a descent. Aircraft X read it back with no callsign. After a minute I notice Aircraft Y had not made a turn which I thought was strange. I verified with Aircraft Y that they were the [the aircraft in distress] and Aircraft X answers 'affirmative' which further diluted the situation. Shortly after Aircraft Y questions 'if they are still with me'. At this point I realized they were not the [the aircraft in distress] and scanned and saw Aircraft X in a right turn and in a descent. My radar Assist and I quickly coordinated with the involved sectors the emergency aircraft and what they were doing. I learned that by me saying 'go ahead' instead of using Aircraft Y's callsign from the beginning may have contributed to the situation. However; when I subsequently used correct callsigns Aircraft X answered for Aircraft Y anyway which is an example of how workload and emergency's have a tendency to add risk.
A Center Controller reported he misidentified an aircraft when the plane did not use their call sign when responding to instructions.