AFTER BEING INFORMED THAT A REQUIRED RII INSPECTION HAD NOT BEEN ACCOMPLISHED ON THE LEFT ENG IDG CHANGE OF A B757-200; A MAINT CONTROL DUTY MANAGER FAILED TO REQUIRE THE ACFT BE STOPPED AT THE NEXT STATION.

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I WORK AS A MAINT CTL DUTY MGR. I WAS WORKING THE DESK WHEN THE LINE MAINT MGR FROM ZZZ CALLED ME CONCERNING ACFT X; A B757-200. A FEW DAYS PRIOR; A ZZZ MECH HAD REPLACED THE L IDG. PER OUR PROCS MANUAL; YOU NOW NEED RII BUY BACK ON ALL 757'S; NOT JUST ETOPS 757'S; DUE TO THE FACT WE HAD BEEN MISSING THE RII ON THE 757 ETOPS FLEET. THE ZZZ MECH DID NOT GET RII BUY- BACK AFTER REPLACING THE IDG ON ACFT X. I OBSERVED THE ACFT WAS OFF OF THE GATE IN ZZZ1; POSSIBLY ALREADY IN THE AIR. I TOLD MR X I WOULD STOP THIS ACFT TO BE CORRECTED. AFTER WORKING SEVERAL OTHER ISSUES THAT DAY; I OBSERVED ACFT; WHICH WAS 1/2 WAY TO ZZZ1 FROM ZZZZ. I CALLED THE DISPATCHER; AND EXPLAINED THAT ACFT X WOULD HAVE TO STOP IN ZZZ1 TO CORRECT THE IDG MISSED RII. I THEN CALLED THE MAINT CTL TECHNICIAN TO WRITE A PRIORITY CODE TO CORRECT THE IDG MISSED RII IN ZZZ1. THE ACFT WAS STOPPED IN ZZZ1 AND THE RII WAS ACCOMPLISHED. I DID NOT STOP THE ACFT IN ZZZZ AND CORRECT THE IDG RII ISSUE. THE ACFT; BEING IN A NON COMPLIANCE STATE; SHOULD HAVE BEEN REMOVED FROM SVC IN ZZZZ. AT THE TIME; I SAW NO SAFETY ISSUE WITH THE ACFT; BUT SHOULD HAVE PRIORITIZED THE SITUATION TO CORRECT THE IDG RII.