Date: 201304
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Tower ZZZ
Reporter organization: Government
Reporter function: Flight Data / Clearance Delivery
Reporter qualification: Air Traffic Control Developmental
Human factors: Communication Breakdown
Anomaly: ATC Issue All Types
Detector: Person Air Traffic Control
Result: General None Reported / Taken
Contributing factors: ATC Equipment / Nav Facility / Buildings; Company Policy; Human Factors; Procedure
Primary problem: Procedure

Narrative: Air Carrier X's original clearance was removed from the FDIO system because the pilot's company was planning to file another clearance for the aircraft. Air Carrier X's company then filed a new clearance after the old clearance was removed and disposed. Air Carrier X then accessed the old clearance via PDC a significant amount of time after it was originally removed. The pilot then taxied out; believing this out-dated PDC'd clearance was his appropriate clearance. Ground Control asked Air Carrier X if he had his clearance because the flight strip was not located at Ground Control. Air Carrier X apparently responded that he had his clearance. The problem was he wouldn't have had any new changes from the new flight plan his company filed; but Ground; Clearance Delivery; and the pilot were all blissfully unaware because apparently the company had not told the pilot that they were going to file a new clearance. Ground asked Clearance Delivery (myself) if I had a strip for Air Carrier X. I did and delivered the strip to ground. The strip was unmarked at flight data; but it is fairly common for a PDC's strip to be unmarked at clearance delivery because of the volume of traffic ZZZ handles and the amount of strip marking the Tower requires. While issuing PDCs; or verbally issuing clearances to large groups of aircraft; one may go unnoticed and fall into the unissued column at Clearance Delivery. Ground will then have to ask Clearance for the strip and it will be delivered at that time. The clearance became available while I was on break and could have been issued at that time so I gave the strip to Ground. Little did I know at the time; the route after the PDR on the strip could have been different from what the pilot had as a result of the pilot pulling up the old clearance via PDC. There was no full route required for the new clearance per what was on the flight strip and the pilot was not informed by the company of a new clearance. Recommendation; there are several correctable issues presented by this event. Primarily; old clearances should not continue to be available via PDC after the clearance has been removed from the system. This is a simple; obvious thing in my opinion and I can not believe that it has not yet been implemented. Second; the company should have a better checklist when changing flight plans; it's absurd that a pilot can be given multiple flight plans for the same route of flight or destination and it always creates more work and a safety hazard for everyone involved; even when clearance delivery and the pilot are aware of the situation. As far as I know; the outcome of this situation was relatively harmless; but it could definitely pose a serious safety risk and even in this situation the pilot could have flown a different routing from what was filed after I had left.




Synopsis: Tower Controller described a very confused clearance event pointing out the potential for errors when companies change a requested route but do not notify the flight crew.