An engine for use in operating an aircraft is disclosed, the engine comprising a decomposition chamber configured to decompose into at least one combustible constituent element a first chemically unstable substance in the presence of a catalyst, wherein the decomposition of the first chemically unstable substance releases a first amount of heat; a first turbine configured to accept the constituent elements and the first amount of heat from the decomposition chamber and thereby rotate; a compressor rotationally connected to the first turbine, and configured to compress air when the first turbine rotates; and a combustion chamber configured to accept the compressed air and constituent elements and combust the combination, substantially regardless of an altitude above sea level and ambient air pressure, and output the combustion products into a power turbine, causing it to rotate, whereby the rotation of the first turbine and/or the power turbine rotate a propeller rotationally coupled to the first and power turbines. Alternately, a nozzle can be used in place of the power turbine, thereby creating a jet engine.