Regional Jet 200 ER/LR (CRJ200)
Air Traffic Control Fully Certified
Communication Breakdown
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
General None Reported / Taken
Human Factors; Company Policy
Flight ABCD and Flight ABCG; Flight ABCD entered my airspace and I cleared him direct JAMMN intersection. Flight ABCG who was just checking on took the clearance. A few minutes later I noticed that Flight ABCD was not turning and I was going to pass very close behind traffic that he would have passed well behind had he made the turn to JAMMN. I queried the pilot and she said that she had never been given the clearance; I looked around and noticed that Flight ABCG was off of his route to the West; he keyed up about that time and said that he had taken the clearance; I put him back over MFL with an expected clearance to JAMMN later. I fear that something serious; accident/midair is going to be required before [Air Carrier Company] does anything to mitigate this issue.
ZLC Controller voiced concern regarding the same company; similar call sign issue that led to a turn by the wrong aircraft. The reporter fearing serious safety implications if this issue is not addressed by the company.