Maintenance messages are notifications that engineers receive from the automated computer system in the engine that tells them the current health of the engine after every flight.
The engineer reviews this and decides if and when a maintenance action is required. If it is a serious event, the airplane is not allowed to take off until it is repaired. Otherwise, the repair can be scheduled for a later date.
This is a reactive process where the engineer reacts to the maintenance messages, which means there are problems with planning and resource allocation.
Airline plans for the repairs, on areas such as planning aircraft to be on the ground, resources to do the work, component to be taken off and replacement. This could cause delays, fly resources to the location for the repair, incurring time and cost.
When a fault happens, something else is likely to fail very soon. We want to help the airline prepare and pre-empt component failure.