Flight intent refers to the information which describes the trajectory to be flown by an aircraft considering the operational context in which the flight take place and the user preferences to be fulfilled along the whole trajectory. In previous work, the set of rules which ensures the generation of valid instances of flight intent was structured as a formal language, the Flight Intent Description Language (FIDL). This paper extends these concepts to a higher level of abstraction, the mission level, and presents the architecture and tools used to generate flight intent from the mission intent expressed in a formal language. The core component of this architecture is a planner that takes the mission intent sentences as inputs and computes a high-level plan in a multi-vehicle context to achieve the goals commanded. The architecture and resulting workflow are illustrated with a surveillance mission to be executed by a fleet of UAS equipped with different payloads.