Date: 201405
Local time of day: 0001-0600
Location: ZLA.ARTCC, CA
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZLA
ATC / advisory: Center ZLA
Reporter organization: Government
Reporter function: Trainee; Enroute
Reporter qualification: Air Traffic Control Developmental
Human factors: Communication Breakdown
Second reporter function: Instructor; Enroute
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance
Contributing factors: Chart Or Publication; Procedure
Primary problem: Procedure

Narrative: I was training on the R-side at sector 25/28 when my trainer and I observed Aircraft X off course.  I immediately took action to correct this route of flight and get him going in the right direction.  When we asked him; he said he originally filed WAGES...FLW.TANDY3.SNA; however; he was rerouted via the OFFSHORE7 SXC transition.  Once he acknowledged the route he had been given; he asked; 'Did we screw that up?'  We took down the aircraft information and forwarded it to our FLM.  This problem seems to be happening on an ever-increasing basis with no one carrier flying the route improperly more frequently than another as far as I have seen.  I would recommend an investigation into what the reason for the FMS's of certain aircraft (assuming that's the problem) are taking these aircraft off course in the same general type of deviation to the east of course.  As I mentioned; no aircraft type or company seems to be more frequently deviating than the other.  My only other thought would be that the way the pilots receive their clearances may be confusing or proper confirmation of receipt is not obtained.


Second narrative: I was the trainer at R25/R28. Aircraft X was routed over MCKEY; on the OFFSHORE to BENET. Just south of MCKEY; I observed Aircraft X change course to the east.  Since we have had several aircraft on the OFFSHORE or COAST  deviate east towards FLW; I brought the aircraft's turn to my trainee's attention quickly.  He recognized the issue and gave Aircraft X a reroute back onto the correct route of flight.  During the next several minutes; I tried to ask the pilot where he was navigating to and how he came to understand that as his route.  He said that the company had filed MCKEY FLW and he was issued the OFFSHORE later. Then he asked if they had messed that up. I responded that the OFFSHORE was right but advised him that the OFFSHORE to SXC was MCKEY DAISY BENET SXC; and that FLW shouldn't have been on his route of flight.  Then I gave him the facility phone number so that he could give a better report of what happened and how the confusion occurred. I'd recommend a full investigation into what issues are causing this to be a recurring issue.  Over the past two weeks; I'm aware of at least four times that aircraft on the OFFSHORE or COAST have turned around MCKEY towards FLW or FIM.  Maybe there is an issue with aircraft FMS or with how these pilots are being given the routing on the ground or in the air from NORCAL or ZOA.


Synopsis: ZLA instructor and Developmental report of incorrect routing not particular to one airline or aircraft type they are seeing more often.