Abstract: A high speed, high-altitude jet aircraft engine operable as a ram-jet and/or turbo-jet using a single combustion chamber in a main housing receiving compressed air and also a variable flow of ram air bypassing the compressor. Primary and secondary burners in different parts of the combustion chamber produce respectively a major high temperature portion of burnt gas exhausted direct through a main nozzle and a minor lower temperature portion ducted off to drive the turbine which is in a side housing, the minor portion being exhausted through a subordinate nozzle.