## 1 Introduction  
The concept of air-to-air or aerial refueling has existed for over a century and it provides significant benefits by increasing the range and flight time of the aircraft [1]. A series of refueling engagements increases the range and flight time of an aircraft to such a point that human limitations become the limiting factor of the aircraft, as prescribed by the Federal Airway Administration (FAA) [2] or the applicable service instruction. With the use of remotely piloted aircraft (RPA) or uncrewed aircraft (UA), crew limitations no longer exist, and aerial refueling can dramatically extend mission capabilities for military use, as well as potential applications for civilian use [3]. Given the strategic advantage aerial refueling provides, aerial refueling has been used for military operations for decades. Due to the cost of integration of aerial refueling systems, the requirement for close formation flying, and the safety risks associated with the task, aerial refueling has predominately been limited to military operations only. During operations in support of Desert Storm, the United States Air Force (USAF) flew nearly 15,000 sorties dedicated to aerial refueling in which their fleet refueled approximately 46,000 aircraft with approximately 700 million pounds of fuel [4]. The requirement to refuel will only increase in future conflicts as standoff ranges for tankers increase due to kinematic capabilities of the weapon systems defending a hostile strategic location. Studies have also been accomplished to examine the potential benefit of conducting aerial refueling for civilian airline operations. A study conducted in 2006 showed that civilian aircraft could see fuel savings of approximately 30-40% while being able to employ smaller, more efficient aircraft to complete longer range missions [3]. Secondary benefits of this include decreasing the size of runways required for aircraft that could aerial refuel, which would drastically increase the flexibility of airlines to provide services to smaller airports [5]. An increase in aviation infrastructure and additional training for pilots would be required to create, train, and manage a civilian tanker fleet for airline operations, similar to the recommended military qualification program provided by the North Atlantic Treaty Organization (NATO) [6]. It would also be necessary to change current aircraft separation requirements while reassessing and accepting the risks of having an aircraft carrying hundreds of people fly in close formation with another aircraft. Policies for fuel requirements that would facilitate travel to the nearest divert in the event of an unsuccessful engagement or \"sour tanker\" (a tanker unable to transfer fuel) would need to be developed as well. Finally, understanding the likelihood of and severity of cascading delays throughout a global network of flights when an airline cannot complete aerial refueling would need to be accounted for in a resilient airline scheduling program [7]. Advancing technologies provide promise for the use of automated air-to-air refueling (A3R). As technology advances, A3R is expected to overcome the traditional limitations of aerial refueling associated with aircraft handling and pilot skills. A3R is synergistic with the increasing use of UA or RPA, and A3R increases the capabilities for military applications, as well as the potential for future civilian applications with small Unmanned Aircraft Systems (sUAS). For nomenclature, the term UA (used by the United States Navy (USN)) will be used for the remainder of this paper and will encompass UA, RPA (used by the USAF), UAS, and sUAS (used in Part 107 operations [8]). The USN published their vision for Naval Aviation in the 2030-2035 timeframe and a heavy emphasis was placed on the importance of Crewed UnCrewed Teaming (CUC-T) [9]. In the near future, the USN looks to deploy their first aircraft carrier-based UA to support tanking and information, surveillance, reconnaissance, and targeting (ISR-T) with the MQ-25 Stingray [9].