LARGE TRANSPORT FO ACCEPTED CLRNC FOR ANOTHER DEST AND ENTERED IT INTO FMS. ENTRY OF THE ROUTE WAS NEITHER COMPLETED NOR CHECKED BY THE CAPT BEFORE TKOF. ATC INFORMED THE FLT CREW OF THE NAV ERROR WHILE AIRBORNE AND THE ROUTE OF FLT WAS CORRECTED.

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WE WERE FLYING A CHARTER TRIP AND UNDER NO TIME CONSTRAINTS OTHER THAN THOSE IMPOSED BY THE CAPT AS THE LAST LEG OF THE TRIP WAS AN EMPTY LEG. I CALLED ZME TO OBTAIN A CLRNC AND A VOID TIME. MEMPHIS ISSUED A CLRNC TO ZZZ1 AS FILED; ETC. I WAS HOLDING A FLT PLAN TO ZZZ1 AND ZZZ2 JUST DIDN'T CLICK AND I BEGAN TO PROGRAM THE FMS AND GPS FOR THE ZZZ1 RTE. WHILE BEGINNING TO PROGRAM THE FMS; THE CAPT ENTERED THE COCKPIT AND WANTED TO START ENGS. I ASKED TO FINISH PROGRAMMING THE FMS AND THE CAPT SAID WE HAVE TO GO; PROGRAM IT IN THE AIR. WE STARTED ENGS AND BEGAN TO TAXI. I CONTINUED TO ENTER THE FLT PLAN AS THE CAPT LINED UP FOR TKOF. I ASKED AGAIN TO LET ME FINISH PROGRAMMING THE FMS AND THE CAPT PUSHED UP THE PWR FOR TKOF. I STOPPED USING THE FMS AND MADE THE PROPER CALLOUTS FOR TKOF AND CLB AS THE PNF. WHILE TALKING TO ZME; THE CAPT TRIED TO HAND FLY AND LOAD THE FMS AND ENDED UP DELETING WHAT I HAD PARTIALLY ENTERED. I NOW SCRAMBLED AND MANAGED TO GET AN INITIAL HDG TO THE VOR ON OUR FLT PLAN. JUST AS THAT HAPPENED; ATC INQUIRED AS TO OUR HDG AND ISSUED DIRECT TO MCB VOR. I AGAIN GOT A HDG OFF THE GPS AND GAVE THE CAPT A HDG TO FLY. ATC NOW SAID PROCEED ON COURSE AFTER MACOMB. I TOLD ATC MCB WASN'T ON OUR FPR. ATC AND I DISCUSSED IT AND FOUND OUT THAT ATC HAD ISSUED THE WRONG CLRNC TO THE WRONG PLANE. WE WERE VECTORED AROUND TFC WHILE IMC AND THEN REROUTED DIRECT TO ZZZ1. I THEN PROCEEDED TO GET THE FMS PROPERLY SET UP AND NAVING TO ZZZ1. THIS WHOLE THING COULD HAVE BEEN AVOIDED HAD THE CAPT NOT HAVE BEEN IN SUCH A HURRY TO GET TO OUR LAYOVER. THERE WAS NO NEED TO TAKE OFF WITHOUT THE FLT PLAN BEING LOADED EITHER. HAD I NOT BEEN SO RUSHED I MAY HAVE NOTICED THAT I ACTUALLY WROTE DOWN THAT WE WERE CLRED TO ZZZ2; INSTEAD OF RAPIDLY TRYING TO LOAD THE FMS OFF THE COMPANY FLT PLAN. SHORT OF TRYING TO ABORT THE TKOF THERE ISN'T MUCH MORE I COULD HAVE DONE TO GET MORE TIME BEFORE TKOF. THE FE ALSO OBJECTED SAYING; 'JUST GIVE HIM A SECOND TO FINISH.' HE TOO WAS IGNORED BY THE CAPT. WE BOTH WERE LECTURED IN CRUISE ON WHY HE DIDN'T WAIT AND HOW IT WASN'T DANGEROUS WHAT HE DID.