Learjet 31
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2.6
Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; General Flight Cancelled / Delayed
Airspace Structure
I was working Arrival sectors combined. It was a busy and complex session with numerous arrivals; lots of VFR targets; practice approaches in and through my airspace. Aircraft X checked in on frequency descending for BFI and I already knew that I would be issuing many traffic advisories thanks to how many I had to issue to the preceding BFI arrival. Once I got Aircraft X down to 2200 feet and in a position to turn towards BFI I scanned and saw a couple of VFR targets that might conflict with the base turn. Aircraft X had reported one of them in sight previously on the descent; so I asked if he still had the traffic in sight; but he did not. Instead of creating a direct conflict with the VFRs; I elected to give Aircraft X a left 360 to bring him back to the final approach course. This abnormal maneuver was caused by the presence of VFR aircraft in proximity to the BFI arrivals. Aircraft X landed without incident.While the VFR targets in proximity to Aircraft X were further away from the Final Approach fix than some of my previous reports; they are still transiting a very busy segment of our airspace at altitudes which put them in direct conflict with our IFR arrival traffic to BFI. This was not a slow moving VFR aircraft either. The target was at 2000 feet and showing 200 knots groundspeed on the radar. I later observed the target enter PAE's Class D airspace and was able to ask the tower controller for a callsign and type which was a [high performance aircraft].Something needs to change. The VFR aircraft are transiting a very narrow; busy corridor of airspace and are doing so without any communication with ATC. It is simply unsafe. The VFR aircraft in this area at the very least need to be in communication with ATC so that we can assign; as necessary; altitude restrictions ensuring the safety of all the aircraft involved. The solutions are not hard and while they are potentially more restrictive to VFR aircraft the bottom line is that what happens day in and day out in that airspace as it exists and operates now will eventually result in a very bad accident.
Air Traffic Controller reported the need to vector an aircraft off the final approach course to avoid fast moving VFR traffic in the area of Boeing Field .