B757 Undifferentiated or Other Model
Flight Crew Last 90 Days 200; Flight Crew Total 8800
Confusion; Situational Awareness
Deviation / Discrepancy - Procedural Other / Unknown
Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; General Maintenance Action
Human Factors; Procedure
[I] arrived at aircraft and all things were proceeding normally.  Auto initiation of the ACARS went as normal with flight [number and departure and arrival stations] all showing and the automatic messages (PDC ATIS RELEASE VERIFY FIT FOR DUTY) were received.  The route was not automatically sent for and when manually requested the route would not down link to the aircraft. Also any FMC or performance data would not download only returning SCAP ERROR.  At this point maintenance was called and a defect was entered into the logbook. After conferring with maintenance Dispatch and Duty Manager the ACARS was deferred with allowance to use it's working functions and we would continue just loading manually the route and winds after the winds would not downlink to the route when requested.  Dispatch had to send us the runway data because it would not downlink. We then departed and all proceeded normally until at cruise and approaching Moncton airspace and CPDLC would not log on and then when trying to get our Oceanic clearance it returned the message AIRCRAFT REGISTRATION ERROR.  At that point I look at flight plan and realized that the flight plan had a different N number than the aircraft. We looked at all the paperwork and everything (maint PDC final weights) was for [our] aircraft but the flight plan was for [a different] aircraft.  There was a plane change at some time but we still showed release 1 and release 1 on the release verify.  We contacted dispatch and they updated our flight plan and registration and we were now able to logon to CPDLC and get our Oceanic clearance by datalink. The flight then continued to destination without any further problems. After looking at this after it happened my thoughts are that having auto init pull the right flight info into ACARS and the [N number being very similar to the flight number] made me think the flight plan was correct along with release 1 still showing current on the release verify. Getting caught up in the maintenance process of troubleshooting and then deferring the ACARS and then proceeding manually for the flight contributed to simply not checking the nose number on the flight plan.  This is one simple check that I won't forget especially if the route or FMC/FMS data link functions don't seem to work or better yet in flight planning in operations.
B757 First Officer reports being unable to use the ACARS during preflight to initialize the FMC and obtain the flight plan and winds. Maintenance defers the ACARS and the flight departs. Approaching Moncton airspace CPDLC would not log on and when trying to get the Oceanic clearance it returned the message AIRCRAFT REGISTRATION ERROR. It is discovered that the N number on the flight plan does not match the number of the aircraft they are in.