Date: 201907
Local time of day: 1201-1800
Location: ZLC.ARTCC, UT
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Airspace: Class E ZLC
ATC / advisory: Center ZLC
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Situational Awareness; Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance
Contributing factors: Aircraft; Airspace Structure; Human Factors
Primary problem: Human Factors

Narrative: I was working when a VFR aircraft southeast of the airport at 12;000 feet westbound was transiting westbound.  A [Aircraft X] checked on climbing off and was in conflict with this aircraft.  The VFR aircraft was not in radio contact with myself or Tower.  Later (north of the airport) I spaced then shipped the first aircraft (can't remember the call sign) to Tower then noticed a VFR aircraft west of the localizer heading toward the airport.  I noticed he was going to be close to the aircraft I had just shipped to Tower frequency and wished I was still talking to give him a heads up of the VFR aircraft's position.  I considered calling Tower but assumed the aircraft was in radio contact with the tower (which he wasn't) and inbound to land.  I noticed the VFR aircraft dive out of the way of my first arrival.  I left the second arrival on a heading a few more minutes before turning him to downwind for the ILS Approach because I wanted space in case a TCAS RA with the VFR forced the first arrival to break off his approach.  After clearing the aircraft for the ILS; I informed him of the VFR traffic which took me completely by surprise when he didn't continue southbound to the airport but turned northbound directly at a fix on the ILS Approach and started climbing.  I knew the weather was clear so I asked them if they wanted to switch to a Visual Approach so he could safely deviate from the fix the VFR was over.  I thought the 2 aircraft were going to hit over the fix so I cleared the arrival to deviate left even though he was on an instrument approach below the Minimum IFR Altitude. The pilot then switched to a Visual Approach. The same aircraft then continued to the lake north of the airport; then turned to the airport; flew directly over the airport and into the departure path while never talking to Tower. We must get an airspace classification around this airport forcing the VFR aircraft to be in radio contact with Tower.  Every day we see many near midair collisions with VFR aircraft sightseeing around the airport while not in radio contact with anyone.  We do our best but this is a very tricky airport since the high terrain all around leaves us little to no options for resolving conflicts below 16000 feet.  This years overdue and we will have a midair collision with a VFR aircraft and an IFR arrival near the airport.  Failure to immediately get an airspace classification around this airport forcing these VFR aircraft anywhere near the arrival/departure corridors to be in radio contact with Tower or Center is negligence on the part of the FAA.




Synopsis: A Center Controller reported an unidentified VFR aircraft repeatedly flew into conflictions with a departing and then an arriving aircraft.