There is an increasing trend in developing hydrogen based electrified aircraft propulsion systems to achieve net zero emissions from air transportation.  In order to achieve highest power density, cooling the electrical systems using cryogenic hydrogen and also using the same liquid hydrogen as fuel provides highest power density and efficiency of the overall system.  In this presentation, different types of architectures under development including hydrogen engine and fuel cell based propulsion are presented. The cryogenic cooling architectures and storage of liquid hydrogen will also be introduced. The work being done by various companies based on the cryogenic cooling of aircraft electric propulsion system is presented.