Hydrogen is increasingly making its way into the aviation industry as an opportunity to reduce emissions. Liquid hydrogen fuel cell aircrafts represent a promising technology to pursue the path toward decarbonization. Hydrogen holds great potential as a means of generating electrical energy and powering air transportation; however, it also poses significant challenges to overcome and stringent requirements to be met to reduce associated risks. Safety concerns are indeed a crucial aspect that greatly influences architectural choices. The thesis aims to analyse the safety aspects of a liquid hydrogen PEM fuel cell regional aircraft with a Model-Based System Engineering (MBSE) approach. A reference aircraft is taken into consideration to execute a safety assessment process, identifying potential failure conditions that could compromise flight safety.