Mini UAVs in the ≺20 kg category are widely operated by military and civilian organizations, usually for surveillance purposes, and many are electrically powered for low acoustic and infra-red observability. Despite recent improvements in Lithium Polymer battery technology, endurance is still usually limited to around 1 hour for fixed wing vehicles. For operational reasons, it is desirable to increase endurance and fuel cells can provide the high energy density necessary to do this.Many examples of PEMFC (Polymer Electrolyte Membrane Fuel Cell)-powered UAVs have been flown in recent years, all relying on a supply of hydrogen on board the UAV, giving the usual safety and weight concerns surrounding hydrogen storage. Solid oxide fuel cells (SOFCs) operate at a sufficiently high temperature to allow some flexibility in fuel source; in particular microtubular solid oxide fuel cell (mSOFC) stacks have been developed that run on methane and propane, gases that are easier to store and more readily available than hydrogen. mSOFC technology also offers the potential for higher efficiencies than PEMFCs.Some examples of mSOFC-powered UAVs do exist, but these are aircraft developed and flown in an R&D context, not operational vehicles. This project aims to surmount and document the issues surrounding integration of an mSOFC power system into an existing UAV used in its operational environment. It also serves to provide a stimulus for the further development of mSOFC technology, which shows good potential but currently lags PEMFC technology by a number of years.This paper presents initial modeling results from a 3-year project to integrate a propane-powered microtubular solid oxide fuel cell power system into an existing (and operational) electrically powered mini UAV.