CREW OF MDT FLEW ENTIRE FLT WITH ACFT OTHER THAN THE ONE NAMED IN THE FLT RELEASE.

Narrative

UPON ARR AT SPOKANE ARPT; I NOTED THE DEP BOARD SAID FLT ABC; GEG-XYZ; DEPARTS GATE X. AT GATE X; THE AC-1 AGENT WAS WORKING THE FLT GEG TO XYZ. SHE DID A SECURITY CHK ON ME AND CONFIRMED I WAS FLYING THIS FLT. I WENT DOWN TO THE ACFT AND NOTED THAT THE FLT ATTENDANT LOGBOOKS AND ACFT LOGBOOKS WERE ON BOARD AND MATCHED THE SHIP NUMBER. THEY DID. I REVIEWED LOGBOOKS AND THEY WERE OK. I USUALLY CONFIRM SHIP NUMBER ON THE RELEASE AS WELL; BUT FAILED TO DO SO THIS TIME. ALL FUEL DATA; ROUTING DATA; MEL DATA WERE CURRENT AND MATCHED OUR FLT. THE ACFT WE WERE IN; COMPARED TO ACFT WE SHOULD HAVE BEEN IN; ARE THE EXACT SAME TYPE; SAME SIZE AND SAME ENGS. ALL THAT DATA MATCHED; INCLUDING PERFORMANCE. INFLT; 1/2 WAY TO OUR DEST; WE GOT AN ACARS THAT STATED FLT ABC SHOULD BE FLT ABD. THE CAPT AND I REVIEWED EVERYTHING WE DID FROM THE TIME WE GOT TO THE ARPT TO PRESENT AND FINALLY WHILE REVIEWING THE RELEASE; DISCOVERED THE ACFT NUMBER WAS WRONG. WE HAD ARRIVED AT THE RIGHT GATE; FOR THE PROPER FLT TO THE PROPER DEST. WE HAD THE CORRECT LOGBOOKS FOR THE CORRECT AIRPLANE. WE HAD PERFORMED ALL THE PROPER FUNCTIONS EXCEPT FAILING TO NOTE THAT FLT OPS HAD FAILED TO PUT THE PROPER PLANE AT THE PROPER GATE. FLT WAS COMPLETED UNEVENTFULLY.