In an effort to develop environmentally progressive technologies for aerospace applications, Boeing researchers and industry partners throughout Europe conducted experimental flight tests in February and March 2008 of a manned airplane powered only by a fuel cell and lightweight batteries. The Boeing Fuel Cell Demonstrator Airplane used a Proton Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electric motor, which is coupled to a conventional propeller. The fuel cell provided all power for the cruise phase of flight. During takeoff and climb, the flight segment that requires the most power, the system relied on lightweight lithium-ion batteries. This aircraft is now displayed in the Future Of Flight Aviation Center in Everett, WA.