Air segment guidance and control for the Bi-Modal Unmanned Underwater/Air System. The Bi-modal unmanned Underwater/Air System (BUUAS) is a vehicle designed in the RMIT University and able to perform a particular Underwater/Airborne mission profile, with the purpose to carrying airborne surveillance mission with reduced exposure risk with respect to its submarine mothership. The vehicle assumes a dual aerodynamic configuration for the two different phases of the mission. In order to investigate the guidance and control characteristics of the vehicle, a simulator has been implemented. Particular attention has been given to the presence of the Y-tail configuration, featuring an anhedral angle, and to the water-to-air transition phase, where the wing is deployed by changing its sweep angle.