nicolas rivero has been reporting on the issue for the washington post. hank you so much for joining us. what exactly was fueling this flight? nicolas: in this case, it was a mixture of sustainable fuels that was made from waste fats and kind of plant sugars. and, all told, they made it about 70% less carbon than standard jet fuel would. ali: how does this type of fuel get made? nicolas: so sustainable aviation fuels are really broad category of fuels that can be made from a lot of different sources. the main thing is they're not made from petroleum, but they might be made fr crops like corn and soybean. they might be made from used cooking oil. they could be made from sewage or municipal waste. the key part of their definition is no matter what they are, they're not made for petroleum and they emit at least 50% less carbon than standard jet fuel. ali: and what is needed to get this fuel made in addition to, i would imagine, a lot of money? nicolas: one of the issues with this right now is there is very little sustainable aviation fuel in the market. part