The need for alternative fuels to power aviation both commercial and military arises from two main factors -energy security and environmental safe guards. Various researchers around the world are looking at alternate feedstocks and methods to obtain drop in fuel keeping the environmental impact of the whole process in mind. The primary target for all these fuels is to satisfy physical and combustion characteristics of at least existing petroleum derived jet fuel -JP-8 and Jet A. With the present global competition for fossil fuel feedstock and increasing price the energy security offered by nonconventional sources seems very attractive. This paper looks at the physical and combustion characteristics of 1. Biodiesel from hydroprocessing (HEFA) and transesterification and 2. Coal, gas and biomass derived synthetic liquid fuels as aviation fuels. The former has already been used in various test runs and the latter already in commercial use in Johannesburg and makes comparison to find the better option. Finally we take a look at "well to wake" concept of a fuel life cycle to see how practical is their use on large scale and future requirements of the aviation industry to access the possibility of them as a long term alternate to petroleum derived jet fuel.