The High Altitude Platform (HAP) is located on an object at an operational altitude of 18 to 50 kilometers and provides network functions of access network, control plane, user plane, and application services. The HAP can provide communication services to end users cooperating with fixed, mobile and satellite convergence (FMSC), which is the capability that provides services and applications to end users regardless of the fixed, mobile or satellite access technologies being used. This Recommendation specifies the requirements of supporting HAP for FMSC for IMT-2020 networks and beyond, focusing on scenarios, requirements, and security considerations.