Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 26
Conflict Airborne Conflict; Deviation - Track / Heading All Types
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Aircraft; Airspace Structure; ATC Equipment / Nav Facility / Buildings
I had to stop Aircraft X at 10000 feet for traffic. Eventually Aircraft X cleared traffic and I climbed the aircraft to 14000 feet. I did have VFR traffic for Aircraft X. That aircraft was Aircraft Y at VFR/16500 feet on a southbound course to enter W-289. Aircraft Y requested communication transfer to Plead Control and my Assist had completed the transfer of control. I knew I would be keeping Aircraft X at an altitude well below Aircraft Y so I switched communications to Plead Control.I waited until Aircraft X was behind the Aircraft Y and I climbed Aircraft X to 23000 feet. As soon as I climbed Aircraft X I could see Aircraft Y making a right hand turn and wondered why he was turning. I called traffic to Aircraft X and the Aircraft X pilot had the aircraft in sight. The Aircraft Y aircraft continued his right turn and by now had turned more than 180 degrees. I attempted to stop Aircraft X at 15500 feet but Aircraft X said he would stop at 16000 feet. I issued a traffic alert to Aircraft X. Aircraft X reported he was receiving a T-CAS alert and was descending to 15500 feet. Aircraft Y passed directly over Aircraft X and continued northbound. Aircraft X was clear of the traffic and I issued climb to Aircraft X. At that time I noticed Aircraft Y in a left turn and they were turning 180 degrees to the left. I told Aircraft X to disregard the climb clearance and maintain his present altitude which as still 15500 feet. Aircraft Y passed directly over the Aircraft X once again and continued southbound into W-289.Aircraft Y was having trouble with his radios contacting Plead Control so he decided to execute a 180 degree turn until he successfully contacted Plead Control to receive authorization to enter W-289. I wish he would have reported back to my frequency so I could have advised Aircraft Y of traffic. In [more than 20] years of ATC experience that is the closest call I have ever been involved with.Not really sure if I could have done anything different. I am thankful that I saw Aircraft Y make the 180 degree turn so I could at least call traffic to Aircraft X and stop the aircraft beneath Aircraft Y. The pilot should have reported back to my frequency when he made his turn and military pilots need to realize there are many civil and commercial aircraft flying and understand how congested civil airspace is in the en route environment.
A Center controller reported a military aircraft no longer on the frequency turned away from its intended route and toward departure traffic.