Atmospheric pressure 1 Design of experiments 1 Electric aircraft 1 High temperature PEM 1 High temperature PEMFCs 1 High temperature proton exchange membrane fuel cells 1 High-temperature PEMFC 1 Hydrogen 1 More electric aircraft 1 Operating condition 1 PEM fuel cell 1 Pressure and temperature 1 Pressure regulators 1 Proton exchange membrane fuel cells (PEMFC) 1 Readjustment method 1 Voltage variation 1 atmospheric pressure 1 design of experiments 1 fuel cells high temperature PEMFC 1 hydrogen 1 more electric aircraft 1 operating conditions 1 readjustment method 1