Air traffic controllers (ATCOs) are currently constrained by a sector-based competence endorsement model that requires extensive, sector-specific training and limits operational flexibility. To address this, the SESAR project IFAV3 proposes solutions to facilitate service provision flexibility. A fundamental part of achieving this objective is to have a common regulatory framework which allows one to provide a service in a different airspace. The Common Unit Competence Scheme (CUCS) is a unified framework designed to harmonize the endorsement process across Europe. The CUCS is a methodology that aims to create a framework for Air Navigation Services Providers (ANSPs), which emphasizes training, planning and endorsement processes across multiple sector groups and Air Traffic Service Units (ATSUs) while remaining compliant with Regulation (EU) 2015/340 and Regulation (EU) 2017/373. CUCS intends to enhance interoperability and workforce adaptability, being a necessary step towards ATCO’s flexibility to operate across a wider range of sectors. This paper outlines the CUCS methodology, detailing its intended benefits and its limitations, and concludes by presenting a set of practical use cases that illustrates its potential implementation in diverse operational scenarios. The methodology allows any ANSP to implement the operational strategy that best suits its needs, guaranteeing compliance with regulations and favouring greater flexibility in the provision of ATC services.