A gas turbine engine configured to combust, by means of a combustor, a compressed air obtained through compression by a compressor, and drive a turbine with use of high-temperature and high-pressure combustion gas generated by the combustion, the gas turbine engine including: a plurality of air passages through which different portions in the gas turbine engine communicate with one another; and a switching device configured to switch air flow paths between the plurality of air passages, wherein the plurality of air passages are each formed by an air pipe disposed outside a compressor casing, and the switching device is mounted to an outer surface of the compressor casing via a heat insulation member.