A computerised aircraft engine maintenance planning system for maintaining an aircraft engine fleet comprising a plurality of aircraft engines, each engine in the fleet comprising an engine health monitoring system configured to provide data indicative of an incipient fault for a respective engine. The planning system comprises: a fault forwarding sub-system configured to receive indications of incipient faults from respective engine health monitoring systems, the fault forwarding system being configured to identify two or more engines having linked incipient faults; and a queuing sub-system configured to assign each engine identified as having an incipient fault to a virtual maintenance queue position; wherein the queuing sub-system is configured to group engines having linked incipient faults to adjacent queue positions.