A LEARJET 55 WAS OPERATED FOR 26 HRS OVER THE REQUIRED 150-300 HR ENG INSPECTION.

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WE WERE USING A MAINT TRACKING PROGRAM BY LEARJET CALLED 'CIMMS.' WE SEND IN RPTS OF FLT TIME; AND THEY SEND BACK A DATE DUE LIST AND WORK CARDS. LAST MONTH (03/02) THEY SENT US NO WORK CARDS FOR THE COMING ENG INSPECTION; BUT DID HAVE IT ON THEIR DUE LIST. WE OVERLOOKED THE DATE DUE LIST AND WAITED FOR THE WORK CARDS -- BAD IDEA; AS OUR FLYING INCREASED GREATLY AND WE OVER FLEW OUR 150-300 HR INSPECTION BY 26.2 HRS. THIS WAS CAUGHT ON THE EVENING OF 04/SUN/02 WHILE THE PLANE WAS ENRTE FROM ZZZ1 TO ZZZ2. I HAD COME IN TO POSTFLT THE ACFT FOR A MONDAY MORNING DEP. I WAS REVIEWING DATE DUE LISTS WHILE WAITING FOR THE ARR. WE IMMEDIATELY COMPLETED THE INSPECTION WITH NO DEFECTS PRIOR TO ITS NEXT DEP. WE NOW HAVE AN UPDATE MAINT DUE BOARD ON THE WALL THAT NOT ONLY GIVES THE NEXT DUE INSPECTION (WE HAVE HAD THE INSPECTION BOARD FOR A WHILE) BUT NOW IT SHOWS THE HRS LEFT TILL NEXT INSPECTION; AND EVERY MONTH 3 SEPARATE PEOPLE WILL REVIEW THE DUE LIST AND SIGN OFF AS TO WHAT IS DUE AND WHEN IT IS DUE; SO THAT THIS MISTAKE DOES NOT HAPPEN AGAIN.