Date: 201502
Local time of day: 1201-1800
Location: ZDV.ARTCC, CO
Flight conditions: Mixed
Weather elements / visibility: 3
Light: Daylight
Aircraft: Small Transport; Low Wing; 2 Turboprop Eng
Operator: Air Taxi
Operating under: Part 91
Flight plan: IFR
Flight phase: Initial Climb
Airspace: Class E ZLC
ATC / advisory: Center ZDV
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Communication Breakdown; Distraction; Situational Awareness; Troubleshooting
Second reporter function: Instructor; Pilot Not Flying
Anomaly: ATC Issue 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 Separated Traffic; Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: Oakland Flight Service call via ringline to request clearance for Aircraft X from 'Rawlings' airport to [a Denver area airport] and would need three minutes on the ground.  I found no flight plan in the system; Flight Service said he'd call back.  A few minutes later he called; just as the flight plan populated in EDST; from RWL; Rawlins Airport via direct TOMSN.TOMSN6.ZZZ.  I issued clearance from Rawlins to ZZZ; with 'climb and maintain 170; expect FL250 five minutes after departure' and a clearance void time; if not off by XX00 to advise not later that XX+05 of intentions.  I don't remember the beacon code offhand.Not long afterward I noticed a XXYY code pop up in Salt Lake Center's airspace; climbing and appearing to come towards my sector from Worland Airport; WRL.  Nothing in EDST matched an airplane coming from there; but the code matched the present assignment to [last three of previous discussed aircraft]; whose track I had created over RWL to wait for the departure.  At this point it occurred to me that somebody might have confused RWL and WRL; just as Salt Lake initiated handoff and the track over RWL auto-acquired onto the handoff aircraft.  At this point I called Salt Lake to inquire if the aircraft really were Aircraft X; and; if so; how he had checked on with the sector.  I was told it was [same last three numbers]; he couldn't get Denver Center on the assigned frequency (132.1; the departure frequency I had assigned for the clearance out of RWL); so he had gone to the Salt Lake frequency and checked on looking for clearance.  The Salt Lake controller had issued clearance; believing the aircraft to be the usual VFR departure picking up an IFR clearance; and was not aware of any other issues in regard to the aircraft.When the [last three as the previous filed aircraft] checked on I was able to determine that he had received clearance through Oakland Flight Service; but had not been able to reach Denver Center and so went over to the Salt Lake Center frequency.  This pilot is experienced and familiar with the area.The most serious immediate problem is that this aircraft departed believing he was operating IFR out of an airport where the responsible controller had no knowledge of the operation; with all the potential risk that entails.  It is clear something in the communication between the pilot and Flight Service did not meet standards; and that the Oakland Flight Service Station had no familiarity with the airports or airspace for which he was requesting authorization for IFR operations.It is difficult to know how address readback errors; to which category these events clearly belong; other than with education.  There appears to be a certain deficiency in the Flight Service Station's operation; particularly with respect to familiarity with the area of responsibility.


Second narrative: After Engine Start at WRL; Worland WY; attempted to call Seattle Center on the ground at WRL; we had no response after several attempts.  Therefore; I called FSS on my cell phone to obtain our clearance and release.  FSS stated they had no flight plan on file so the briefer offered to file one for us which he did.  He returned with a clearance and release which included the instructions to contact Denver Center on 132.1 after departure.  We accepted the clearance and departed WRL and attempted Denver Center without success so switched to Salt Lake as published on the instrument chart and as we had used going into WRL the day before.  That attempt was successful and it seemed apparent that Salt Lake was expecting us.  We were immediately in radar contact and they gave us a transponder code different from what our clearance had been.Our IFR flight plan had been filed via FltPlan.com who reported back to us that the flight plan had been submitted and filed; WRL to ZZZ.Subsequently in conversation with Denver Center; it seemed there was confusion about our flight plan.  Our speculation is that; for whatever reason; background noise in the cockpit from the engines; poor cell phone reception; unfamiliarity with the area; the FSS briefer mistook my communication and perhaps thought we were departing out of Rawlins WY; RLW; and didn't understand or misinterpreted my statement we were departing out of Worland; WRL.Our question and confusion is I was under the impression that if a flight plan had been filed by aircraft tail number that tail number would show up and display whatever flight plan was filed under that tail number.  Our concern or misunderstanding is that when we called FSS; 15 minutes after the flight plan had been filed by FltPlan; it didn't show up in the system and wasn't visible to FSS.


Synopsis: A ZDV Controller and pilot report confusion after the aircraft departs IFR at one airport while the Controller was waiting for the aircraft to depart off of a different airport. The identifiers for the airports are close and caused the confusion.