The main requirements are:
- A valid air traffic controller licence in accordance with Regulation (EU) 2015/340 with at least one of the following licences: ADI, APS, AIR, GMC, RAD
- A valid trainer qualification for on-the-job training (OJTI) or may train on synthetic training equipment (STDI)
- At least 5 years of professional experience as an air traffic controller and at least 2 years of experience as an OJTI
Full job description : https://www.dfs-as.aero/images/pdf_jobs/Freelance_Instructor_for_ATC_Training_EN-Neu.pdf