A Maintenance Planner described the procedures that allowed an A320 deferred item; with three limits for terminating action; to run beyond the maximum flight hour limits for required repairs.

Narrative

I put an override date into our maintenance computer to follow a maintenance item that has three limits for terminating action. The limits are 'C'-check limits of 20 months; 6000 flight hours or 4500 cycles; whichever occurs first. During my review of an A320 'C' check package; I did not notice the deferred item was tracking against 6000 flight hour limit; and instead; put in an override date; to track with the 'C' check. This was not noticed by the Maintenance Planner who was handling the package; during his normal review and processing of the package. From history in our maintenance computer; the Maintenance Planner deleted his deferred item from the A320's package. I do not know what time. By my calculations; the deferred item would have been very close to the 6000 hour limit.A Line Planning Supervisor; was running a search report for records not reconciled for time; when he noticed the deferred item was over time. I do not remember putting this override date in; but we were able to determine that my employee number and terminal were used.Under normal circumstances; if this were my package; I would have noticed the flight hours running out before an over flight occurred and would have notified Line Planning that the maintenance item would not make 'C' check and would need to be routed in; to have this taken care of. Unfortunately; I did not do the regular auditing of the package; once I did the initial review; as I had turned it over to the Maintenance Planner; the Senior Planner. We are required to do a 7-day review prior to adding more maintenance items (to the 'C' check). If this review would have been done; and this deferred item questioned; we would not have over flown this item. We have put into place a process that allows only supervisors and/or managers to put in an override date. In most cases; we initiate a review; similar to an expedited process. An example would be for a 'C' check that is tracking due; but is scheduled to go into check the 10 days later. The technical manual allows calendar driven items to go to the end of the month. Program verifies there are no airworthiness directives (AD)'s; certification requirements (CMR)'s and etc; embedded in the routine 'C' check that will not make the end of the month; and that if cycle or hour limits also apply; that we will not go over on these limits. Once this has been reviewed and approved by all involved; then a report is initiated to change the tracking to the end of the month; thereby no negative tracking will appear in our maintenance computer. We also go through this process with any deferred items already tied to the 'C' check.