A CLBING MD80 FLC STARTS TO PROCEED ON THE WRONG RADIAL OFF OF TIJ; FO. FLT HAD BEEN FILED FOR A PROVISIONAL ARPT; NOT THE NORMAL ONE WHILE ON FREQ WITH MMZT; FO.

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THE FLT WAS SCHEDULED TO FLY LAX-ZLO (MANZANILLO); HOWEVER; ZLO WAS BELOW MINIMUMS TO FILE AS A DEST SO THE COMPANY FILED US TO ACA (ACAPULCO) WITH THE INTENT OF CHANGING OUR DEST ENRTE BACK TO ZLO WHEN THE FORECAST IMPROVED. WE WERE GIVEN 2 FLT PLANS LAX-ZLO AND LAX-ACA. BOTH ENTER MAZATLAN AIRSPACE OVER TIJ THEN THE COURSES DIVERGED. I HAD LOOKED AT BOTH FLT PLANS BEFORE DEPARTING; BUT I DID NOT LOOK CLOSE ENOUGH TO NOTICE THE CHANGE. I FEEL I SAW WHAT I WAS EXPECTING TO SEE. I FLY TO MEXICO A LOT (90% OF MY FLTS) AND IT IS ALWAYS THE SAME RTE REGARDLESS OF DEST (THE FIRST PORTION AT LEAST). THE COMPANY SAID THEY WOULD CALL OVER MZT (MAZATLAN) BUT INSTEAD CALLED US OVER TIJ TO CHANGE OUR DEST. SEVERAL THINGS WERE TAKING PLACE -- CLBING; NEW AIRSPACE; TALKING WITH DISPATCH AND GETTING SOME INFO FROM THE FLT ATTENDANTS. AS WE PASSED OVER TIJ I FLEW OUT THE 145 DEGS ACCORDING TO THE LAX-ZLO FLT PLAN NOT THE 114 DEGS AS CLRED (LAX-ACA). ABOUT 20 MI S I NOTICED THE ERROR AND TOLD THE CAPT (WHO WAS NOW FLYING) TO TURN L FOR THE 114 DEGS. ABOUT 30 SECONDS AFTER THE START OF THE TURN MAZATLAN CTR CALLED TO CONFIRM OUR DEST. WE REQUESTED AND RECEIVED CLRNC TO ZLO VIA 145 DEGS FLT PLAN RTE. WE SHOULD HAVE PAID MORE ATTN TO THE FLT PLAN SINCE THIS WAS A NON STANDARD OP (2 FLT PLANS WITH A DEST CHANGE). ALWAYS REVIEW THE RTE REGARDLESS OF HOW MANY TIMES YOU'VE FLOWN THE RTE BEFORE.