TRACK DEV. CLRNC NOT FOLLOWED DUE TO HABIT PATTERN.

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INADVERTENTLY STARTED FLYING A RTE THAT WE WERE NOT CLRED. FOR THE PAST 8 YRS WE HAVE BEEN REGULARLY FLYING TO 5N4; NC; FROM OKV; VA. OUR USUAL FILED RTE AND CLRNC IS OKV; LDN; CSN; MOL; LYH; AND THE MAJIC ARR. IT WAS AN EARLY MORNING DEP. DUTY DAY STARTED AT XB00 WHICH HAD RPTR UP AT XA00. THIS PARTICULAR DAY; CLRNC WAS OKV; LDN; CSN; MOL; LYH; V143; TO JOIN V20; MAYOS; MAJIC 8 ARR; 5N4. AS MAYOS INTXN IS A PART OF THE MAJIC 8 ARR FROM LYH; BOTH PLTS FAILED TO PICK UP ON THE CHANGE IN THE RTE TO REQUIRE A DIFFERENT RTE TO MAYOS FROM WHAT HAS BEEN DONE FOR THE PREVIOUS YRS. THE FIRST INDICATION OF BEING ON THE WRONG TRACK WAS WHEN CTR INQUIRED IF WE WERE ESTABLISHED ON V143. WE WEREN'T; BUT HAD PROCEEDED ON THE MAJIC 8 ARR FROM OVER LYH. RECEIVED NEW CLRNC FROM CTR. SHOULD HAVE BEEN MORE ALERT WHEN COPYING THE CLRNC. BUT WE WERE RUNNING LATE; DEP WAS DELAYED BY AN IAD EMER. AND FRANKLY; WE WEREN'T REALLY EXPECTING ANYTHING DIFFERENT. GUESS WHEN DEALING WITH ATC THE RTE FROM A TO B SHOULD NEVER BE TAKEN AS A SURE THING.