As the global energy landscape evolves in response to anthropogenic climate change, there is an increasing focus on using sustainable alternatives to conventional fossil-based fuels. In aviation such an alternative is provided by drop-in synthetic fuels which can blended with fossil kerosene to produce a blend that is virtually indistinguishable from conventional kerosene and is fully compatible with existing infrastructure. However, for most of these fuels blending is a crucial part of the process as the fuels are not fully drop-in on their own. This topic is discussed in the following chapter, with a focus on powerfuels.