To mitigate the climate change impact of aviation, jet fuels from bio-based by-products are considered a promising alternative to conventional jet fuels. Life cycle assessment (LCA) is a commonly applied tool to determine the environmental impacts of bio-jet fuels. This article presents both attributional and consequential LCA models to assess an innovative bio-jet fuel produced from potato by-products in the Netherlands. The two models led to opposite conclusions regarding the overall environmental performance of this bio-jet fuel. The attributional LCA showed that this bio-jet fuel could offer about a 60% GHG emissions reduction compared to conventional jet fuel. In comparison, the consequential LCA estimated either a much lower climate change benefit (5–40%) if the potato by-products taken from the animal feed market are replaced with European animal feed or a 70% increase in GHG emissions if also imported soybean meals are used to replace the feed. Contrasting conclusions were also obtained for photochemical ozone formation. Conversely, the attributional and consequential LCAs agree on acidification, terrestrial eutrophication and depletion of fossil fuels. Although the consequential LCA was affected by higher uncertainties related to the determination of the actual product displaced, it allowed understanding the consequence of additional animal feed production. This process was not included in the system boundaries of the attributional LCA.