Aircraft engine

The aircraft engine has one-or multi-stage compressor arrangement (V), downstream combustion chamber (BK), one or multi-stage turbine assembly (HT,NT), compressor heat exchanger arrangement (WV), turbine heat exchanger arrangement (WT) and by-pass unit (BY). The by-pass unit is provided for selectively by-passing or guiding the working medium with respect to turbine heat exchanger arrangement. An independent claim is included for method for operating aircraft engine.