ABSTRACT. In this paper, we present extensions to Unmanned Systems Autonomy Services (UxAS) to handle mission specifications that require a synchronization of task execution. UxAS uses Process Algebra (PA) as a formal language to specify mission requirements for unmanned aerial vehicle (UAV) operations. However, the current implementation of PA in UxAS utilizes assigned semantics which does not guarantee the order of task completion and is unable to provide a mission planning required vehicle-synchronization. To enable the capability of UxAS in operating synchronized mission specifications, we introduce a notion of Synchronized Process Algebra (SPA) which extends PA by adding a synchronized composition operator to the syntax of PA. Such an operator allows us to specify the task’s duration and enforce the next task is executed after the previous one has terminated. Moreover, we provide a new service in UxAS, called Temporal Service (TS) to control the flow of the planning process with respect to timing specifications. We apply SPA and TS to specify and operate the mission specification of a forest fire rescue scenario required the synchronized arrivals of multiple UAVs.