A method for creating ullage in a fuel tank includes the steps of porting NEA into a mixing chamber during descent, exposing the mixing chamber to ambient air and communicating a mixture of NEA and ambient air into the fuel tank. A complementary apparatus to the method includes a mixing chamber for receiving NEA during descent, a port for communicating ambient air with the mixing chamber during descent and a port for communicating a mixture of the NEA and the ambient to the fuel tank.