Softwarized hybrid Terrestrial/Non-Terrestrial Networks (TN/NTNs) will fulfill the requirement of the 3D ecosystem realized by infrastructures beyond the fifth generation (B5G) to efficiently deliver unicast/multicast/broadcast services thanks to their capability of increasing network coverage, capacity, and scalability. Particularly, unmanned aerial vehicles (UAVs) acting as aerial base stations (airborne elements) can cover unconnected areas and assist the terrestrial infrastructure in overcrowded scenarios. This work proposes an access network selection solution for a softwarized TN/airborne environment to satisfy multiple service petitions and optimize resource utilization. The proposal is based on multi-attribute decision-making and cooperative game theory, taking advantage of network slicing and unicast/broadcast capabilities to effectively allocate resources on demand and handle overload situations directly impacting users’ quality of service (QoS). The solution contributes to adequately implementing the upcoming 5G Multicast/Broadcast Services (MBS). The proposed algorithm is tested in a football stadium as a particular use case and validated through network-level simulations.