The paper introduces a conceptual framework that could improve aviation safety performance and the safety performance measurement process. The framework provides guidance on how organisations could design, implement and use a proactive, performance-based measurement tool for assessing and measuring Acceptable Levels of Safety (ALoS) performance at sigma (u) level, a statistical measurement unit. Nevertheless, the framework provides a holistic view on how organisations could set leading performance indicators and monitor metrics on the top of identified root-causes that affect system's safety performance or how to set lagging indicators and feedback metrics on the top of safety outcomes. In fact, the framework adapts and combines classical Quality Management tools, a leading indicators programme and Lean-Six Sigma methodology to formally and continuously improve a stable and in-control safety management process. Finally, the paper underlines the necessity of a new way of thinking for the development of a robust, proactive process for measuring aviation safety performance and system performance variability. (C) 2017 The Authors. Published by Elsevier B.V.