Helicopters and other aircraft are often used to combat fires which cannot be controlled by personnel on the ground and the practice is a fairly expensive one. Various online sources cite to a 2003 statement from the U.S. Forest Service and Bureau of Land Management that those agencies own, contract or lease 1,000 aircraft for aerial firefighting each year at an annual cost of more than $250 million as of 2003. Aircraft can serve multiple purposes in helping to put out large fires by dropping either fire retardant or water to put out the blaze, deliver supplies to ground personnel or provide reconnaissance for large area fires. The state of California, which has dealt with massive wildfires in recent years, has been using aircraft to fight fires since the 1950s when it started using agricultural planes to dump water on fires. In 2016, there was an increase in the percentage of unfulfilled requests for air tankers to fight fires with 13.4 percent of such requests going unfulfilled, but that is down significantly from the nearly half of all such requests going unfulfilled in 2012.