The exploration and settlement of Alaska would not have been possible without the development of the aircraft, which allowed for the influx of settlers into the state's interior, and rapid transportation of people and supplies throughout. However, due to the unfavorable weather conditions of the state, and high ratio of pilots-to-population, over 1700 aircraft wreck sites are scattered throughout its domain. Numerous wrecks also trace their origins to the military build-up of the state during both World War II and the Cold War.