John Heimlich is Senior Economist at the US-based Air Transport Association and explains that US airlines are primarily concerned with the scale of biofuel supply. The biggest concern with biofuel supply is its ability to provide billions of gallons of fuel. Airlines want an alternative to fossil fuels. There is a point at which the cost of biofuels need to drop to below that of fossil fuels and he believes that could be a decade away. So airlines are ready for this option, and sooner would be better than later. After all, biofuels burn hotter and cleaner than fossil fuels. With blends of up to 50/50 approved for testing, airlines are eager to have an energy option whose pricing is stable.