Purpose: This article seeks to address aviation as an emerging biofuel consumer and to discuss sustainability issues and consequences for feedstock production concepts. Biojet fuels have been identified as a promising, readily deployable alternative to fossil-based aviation fuels. At the same time they are highly criticised as their production may have negative social and environmental impacts. Therefore, the paper aims to identify major sustainability issues and assessment challenges and relate these to the production of biojet fuel feedstock. Design/methodology/approach: Two plant oil production concepts are presented that address the sustainability issues discussed. Both concepts are being investigated within the research project "Platform for Sustainable Aviation Fuels". A literature-based overview of sustainability issues and assessment challenges is provided. Additionally, conceptual insights into new plant oil production concepts are presented. Findings: The use of biojet fuels is often hailed as a strategy for the aviation industry to become more sustainable. However, biofuels are not necessarily sustainable and their potential to reduce GHG emissions is highly debated. Several unresolved sustainability issues are identified highlighting the need for improved assessment methods. Moreover, the two concepts presented have the potential to provide sustainably grown feedstock, but further empirical research is needed. Originality/value: This article addresses researchers and practitioners by providing an overview of sustainability issues and assessment challenges related to biojet fuels. Consequences are identified for two plant oil feedstock concepts: catch cropping in temperate regions and silvopastoral systems in tropical and subtropical regions.