 This is a Bloomberg Money Minute. Airlines are looking at sustainable aviation fuel to reduce their carbon footprint. Sustainable aviation fuel can be made from things like fats and greases, oils. That's primarily what we're seeing today. Ryan Spies is managing director of sustainability at Seattle-based Alaska Airlines, and he says a major challenge now is availability. It can be almost like a miracle drug, but that doesn't exist in any quantities that we really need today. And then there's the cost.