This report will examine the different training modes related to trans-national access (TNA) access (physical, remote, hybrid, and virtual) in the context of European research infrastructure projects related to air quality and greenhouse gas measurements. The pilots performed within ATMO-ACCESS have been analyzed to identify factors that contribute to the long-term sustainability of training programs. The reasons why physical attendance may still be required are examined, and recommendations are provided on how to best integrate innovative, flexible training solutions while preserving the core benefits of traditional in-person training.