There have been several fuel cell powered unmanned aerial vehicles (UAV). A Horizon fuel cell UAV set the record distance flown by a small UAV in 2007. The military is especially interested in this application because of the low noise, low thermal signature and ability to attain high altitude. In 2009, the Naval Research Laboratory’s (NRL’s) Ion Tiger utilized a hydrogen-powered fuel cell and flew for 23 hours and 17 minutes. Boeing is completing tests on the Phantom Eye, a high-altitude, long endurance (HALE) to be used to conduct research and surveillance flying at for up to four days at a time. Fuel cells are also being used to provide auxiliary power for aircraft, replacing fossil fuel generators that were previously used to start the engines and power on board electrical needs. Fuel cells can help airplanes reduce CO2 and other pollutant emissions and noise.