Narrative:

I was working a moderate arrival push into the dfw metroplex. During the push the [radar assist position] advised me of a code 4402 (aircraft X) in the vicinity of trl airport climbing out of about 10;000 feet headed south toward the string of arrivals. The code 4402 was climbing toward aircraft Z out of 16;000 feet. I stopped aircraft Z at 15;000 feet and called the traffic to him. Aircraft Z never got the aircraft in sight and I descended him once he was clear of the target. The code 4402 appeared to stop at 14;500 feet. I stopped aircraft Y at 15;000 feet and called the traffic. Then code 4402 appeared to climb to 15;500. I turned aircraft Y 15 degrees right to clear the traffic and continued aircraft Y down to 12;000 feet. After I turned aircraft Y code 4402 turned to the east into aircraft Y. I issued aircraft Y a further right turn to heading 330 and continued to call the traffic. Aircraft Y received a resolution advisory for the traffic and increased his decent rate. At this time I assume the code 4402 saw aircraft Y and made a hard turn to the south. The new heading put the code 4402 toward aircraft a; who was descending on the arrival. I was able to stop aircraft a at 17;000 feet in case the code 4402 climbed from the current altitude of 15;000 feet. Aircraft a saw the code 4402 on his TCAS and eventually got the aircraft in sight. I asked aircraft a if he could make out the type of aircraft and he replied it was a 'fast mover' and 'dark in color.' I started a track on the code and coordinated with ZHU that the code was headed south toward the iah arrival route from the northwest and advised them to use caution. Approximately 2 hours later code 4402 flew back through the sector from the south west still at 15;500. The code 4402 performed multiple 360 degree turns and appeared to land at ZZZ airport. I would contact the operators that work out of ZZZ and advise them of the situation and have them use more caution when performing their 'missions.'

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Original NASA ASRS Text

Title: An unidentified VFR aircraft was maneuvering in the vicinity of main arrival routes to an airport. ATC had to vector and assign altitudes to several air carrier aircraft to avoid the VFR traffic.

Narrative: I was working a moderate arrival push into the DFW metroplex. During the push the [Radar Assist position] advised me of a code 4402 (Aircraft X) in the vicinity of TRL airport climbing out of about 10;000 feet headed south toward the string of arrivals. The code 4402 was climbing toward Aircraft Z out of 16;000 feet. I stopped Aircraft Z at 15;000 feet and called the traffic to him. Aircraft Z never got the aircraft in sight and I descended him once he was clear of the target. The code 4402 appeared to stop at 14;500 feet. I stopped Aircraft Y at 15;000 feet and called the traffic. Then Code 4402 appeared to climb to 15;500. I turned Aircraft Y 15 degrees right to clear the traffic and continued Aircraft Y down to 12;000 feet. After I turned Aircraft Y code 4402 turned to the east into Aircraft Y. I issued Aircraft Y a further right turn to heading 330 and continued to call the traffic. Aircraft Y received a resolution advisory for the traffic and increased his decent rate. At this time I assume the code 4402 saw Aircraft Y and made a hard turn to the south. The new heading put the code 4402 toward Aircraft A; who was descending on the arrival. I was able to stop Aircraft A at 17;000 feet in case the code 4402 climbed from the current altitude of 15;000 feet. Aircraft A saw the code 4402 on his TCAS and eventually got the aircraft in sight. I asked Aircraft A if he could make out the type of aircraft and he replied it was a 'Fast Mover' and 'Dark in color.' I started a track on the code and coordinated with ZHU that the code was headed south toward the IAH arrival route from the NW and advised them to use caution. Approximately 2 hours later Code 4402 flew back through the sector from the south west still at 15;500. The code 4402 performed multiple 360 degree turns and appeared to land at ZZZ airport. I would contact the operators that work out of ZZZ and advise them of the situation and have them use more caution when performing their 'missions.'

Data retrieved from NASA's ASRS site 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.