 Complete the following phrase:  Airlines use futures contracts and derivatives to hedge their exposure to the price of jet fuel. They know that they must purchase jet fuel for as long as they want to stay in business, and fuel prices are notoriously volatile. By using crude oil futures contracts to hedge their fuel requirements and engaging in similar but more complex derivatives transactions, Southwest Airlines was able to save a large amount of money when buying fuel as compared to rival airlines when fuel prices in the U.S. rose dramatically after the 