A fuel cell system that employs a method for increasing stack power ramp up for high power up-transients by decoupling the build-up of stack current density from the cathode side pressure. The system gives the compressor power priority during the power up-transient to quickly provide the proper compressor speed, and therefore the proper air mass flow, for the desired current density of the fuel cell stack. The system also maintains the cathode side pressure of the stack low by keeping a cathode back-pressure valve open. By increasing the cathode input airflow rate to the proper level at the power up-transient, the current density of the stack will increase to the desired stack power level. Subsequently, the back-pressure valve is closed to increase the stack voltage to provide the total maximum power achievable by the stack.