The first ever full scale simulation exercise within DPPI SEE is completed. DPPI FLEX 2023 was held between 23-27 October 2023 in Brcko, Bosnia and Herzegovina with participation of all 10 DPPI SEE member states. The exercise was organized in close coordination with the Ministry of Security of Bosnia and Herzegovina - Sector for Rescue and Protection and Brcko District Department for Public Security. Drone flying operations, data management, solving logistics problems regarding incoming humanitarian assistance and camp management where the topics of the exercise all of them combined in one scenario. The activation of the Union Civil Protection Mechanism was used to coordinate the incoming assistance to Bosnia and Herzegovina. This process was also supported by deploying a EUCPT, again composed of members from the DPPI SEE member states ( and one Liaison Officer from ERCC). The OSOCC had a specific task having in mind the above mentioned operations (drones, logistics, camp management). Therefore 3 cells were created within the OSOCC covering each of the segments. Some of the immediate lessons identified are towards STANDARDIZATION - what is a drone team? technical and personal requirements? FLEXIBILITY - the exercise required splitting of the teams and COMMUNICATION - key element in planning and implementing the exercise especially when new technologies and approaches are implemented.