It is not always possible to repair a system failure before the next flight. The MEL permits the dispatch of an aircraft with inoperative equipment or functions for a limited period of time, and under specific conditions, while maintaining an acceptable level of safety. Current in-service data shows an increase in the number of requests for MEL extension indicating an increase of departures with multiple open MEL items. Even if dispatch under MEL always guarantees an acceptable level of safety, it increases the risk of exposure to multiple failures with their inherent operational consequences. This article recalls the importance of fixing MEL items at the earliest opportunity to reduce this risk of exposure to multiple failures, and provides best practices where MEL extensions are necessary to maintain the highest possible margin of safety.
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