A miniature unmanned aircraft which uses remotely controlled model aircraft components and technology, and has on-board automatic “on-the-fly” fuel and air mixture adjustment enabling high altitude flight. The aircraft, which may have conventional fuselage, wing, reciprocating piston engine and radio frequency operated controls, also has sensors for sensing atmospheric pressure, atmospheric temperature, engine crankshaft rotational speed, engine temperature, and exhaust temperature. A microprocessor aboard the aircraft receives inputs from the sensors and controls at least one servo to adjust fuel and air mixture according to preprogrammed look-up tables and equations to operate the engine at appropriate fuel-to-air ratios for the altitude and other operating conditions.