The types of missions that an aircraft, and more specifically an unmanned air vehicle, can address and the type of goals that can be achieved depend on the performance and features of the aircraft involved in each mission. For example, a rotorcraft can perform confirmation missions hovering over a defined location where a threat has been identified, while a fixed-wing aircraft is more appropriate for surveillance missions over large areas.
However, missions are also constrained by the payload system, which restricts the aircraft performance and can be influenced by some vehicle limitations. The size, shape and configuration of the aircraft are paramount for establishing the payload to be installed onboard, and therefore, influence the types of missions that can be executed by the global system (equipped aircraft). The significant advances in payload capabilities during the past years represent a step forward in the “payload with persistence” direction towards the concept of autonomous UAVs. In this strategic vision the relevance of payload is nowadays the main bottleneck, so it is easy to find serious limitations about how to integrate some specific sensors or devices onboard.
The NATO Standardization Agreement STANAG 4586, under the control of the NATO Naval Armaments Group (NNAG), aims at standardizing the interoperability procedures for cooperative mission executed by a fleet of UAVs. This standard establishes separated levels of interoperability according to the type of mission, vehicles performances and payload capabilities. The payload has a very close relationship with the air vehicle, conditioning its nominal operation and strongly influencing the mission execution. Mission management is designed to control and monitor both the air vehicle operations and also the payload performances, considering the payload “as part” of the vehicle. This standard identifies five levels of interoperability (LOI) to accommodate operational requirements:                Level 1: Indirect receipt/transmission of UAV related data and metadata.        Level 2: Direct receipt/transmission of UAV related data and metadata.        Level 3: Control and monitoring of the UAV payload, not the unit.        Level 4: Control and monitoring of the UAV without launch and recovery.        Level 5: Control and monitoring of the UAV including launch and recovery.        
The respective operational requirements and approved concept of operations (CONOPS) will determine or drive the required LOI that the specific UAV system will achieve. The STANAG 4586 defines payload and payload plan as:                Payload: UAV sensor(s), weapons, chaff, pamphlets, onboard systems, etc., carried onboard which are used to accomplish a specified mission.        Payload Plan: Details of the sensor to be used, or which sensors are to be loaded if multiple payloads are within the UAV capability. At specific points along a route there may be pre-planned sensor operations and the details of these have to be incorporated into the payload plan and associated with waypoints in the route. Available as hard copy for UAV payload loading and for display with or alongside the route plan, action cueing has to be incorporated either for the operator or the UAV depending on system sophistication. Payload planning may includes payload configuration (e.g., payload type and lens size), payload imagery extraction (e.g., desired resolution), and operator commands for controlling both EO/IR and SAR payloads (e.g., zoom settings, depression angle, and focus).        
This standard defines a communication protocol to fulfill, defining different kinds of payloads and operations, in order to achieve interoperability of heterogeneous UAV systems.
Another approach to this problem is the Joint Architecture for Unmanned Systems (JAUS), formerly known as Joint Architecture for Unmanned Ground Systems (JAUGS), which was started in 1998 by the United States Department of Defense to develop an open architecture for the domain of unmanned systems. In order to ensure that the component architecture is applicable to the entire domain of current and future unmanned systems, it was built on five principles: vehicle platform independence, mission isolation, computer hardware independence, technology independence, and operator use independence. The JAUS reference architecture is a component based message passing architecture that defines a data format and methods of communication between computing nodes. The architecture dictates a hierarchical system built up of subsystems, nodes and components, and contains a strictly defined message set to support interoperability. Significant portions of the architecture, including the definitions for subsystem, node and component, have been loosely defined in order to accommodate for the five principles on which it is based.