Airlines seek new ways to save on fuel as costs soar Fuel is an airline's biggest single expense. In 2008, the cost of jet fuel rocketed. Airlines tried to switch to newer generation aircraft, which have more fuel-efficient engines. Source: The New York Times, June 11, 2008 How does a technological advance that makes airplane engines more fuel efficient change an airline's total product, marginal product, and average product?An airline's average product _______. A. decreases B. increases C. does not change D. becomes negative