Date: 201911
Local time of day: 1801-2400
Location: SCT.TRACON, CA
Aircraft: Light Transport
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class E ZLA
ATC / advisory: TRACON SCT
Second aircraft: Light Transport
Reporter organization: Government
Reporter function: Approach
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Confusion; Distraction; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Company Policy; Human Factors
Primary problem: Company Policy

Narrative: Air Carrier Y was on the RNAV arrival landing BUR. I was stepping this aircraft down reference other aircraft in the area. Air Carrier X Flight ABCD was an OXR arrival at 4;000 feet that I was vectoring to final due to the ILS being out of service. I had another OXR arrival that was being vectored to follow and was stepping down reference other traffic. Air Carrier X Flight ABCE was enroute to SBA at 6;000 feet from over VNY. The Controller who was working Air Carrier X Flight ABCE requested direct to the IAF for SBA. I said unable I need him on the route. I was trying to vector Air Carrier X Flight ABCD between several VFR aircraft while trying not to vector too far south to avoid an MVA at 4;300 feet. I switched Air Carrier X Flight ABCD with a last heading of 260; which was read back. Then Air Carrier X Flight ABCD asked if that last call was for Air Carrier X Flight ABCD; which I responded in the affirmative and shipped the aircraft to Approach. At this time I did not realize that Air Carrier X Flight ABCE took the frequency change for Air Carrier X Flight ABCD. When I realized that Air Carrier X Flight ABCE was not on the route as I had coordinated and expected I tried to turn the aircraft twice with no response. I then turned Aircraft X immediately and descended the aircraft to 5;000 feet. He responded and stated that he was receiving a TCAS RA and I issued a traffic alert. In this event I assumed that Air Carrier X Flight ABCE would be on the route that had been coordinated; however the previous Controller issued a heading instead which put the aircraft head on with my arrival. If he had been on the route they would have passed with about 4 miles of lateral separation. I got distracted with my OXR sequencing and avoiding VFRs while trying to vector to final with the ILS OTS. When I noticed the conflict; I had time to save it and tried to turn the Air Carrier X Flight ABCE out of the way; however the aircraft was not on frequency due to him taking his company's frequency change.The first thing that NEEDS to happen is to get the company to change their call signs. I personally have had several incidents with similar sounding call signs with this particular company and all depart around the same time. I have brought this up multiple times with no response. I don't understand why we still allow this to happen. I talked to the Controller working the adjacent sector and he apologized and said that he thought I understood that he put the aircraft on a heading.




Synopsis: SCT TRACON Controller reported an airborne conflict resulting from similar sounding callsign confusion.