The aerospace industry increasingly employs lightweight fibre-reinforced composites, predominantly synthetic fibres like carbon and glass. However, the current synthetic fibres produce a considerable amount of carbon dioxide (CO2) in the process which conflicts with the ongoing trend of low carbon emissions. Hence, it brought to the initial idea to investigate the possibility of using plant-based fibre as a substitute for synthetic fibres, focusing on sustainability. The plant-based fibre certainly demonstrates high CO2 absorption during cultivation and requires less processing energy compared to the reinforcement fibre, so it should have lower CO2 emissions compared to the synthetic fibre. This study will demonstrate the mechanical properties of high-potential plant-based fibres grown and manufactured in Thailand, such as pineapple leaf (PALF), hemp bast, and agave leaf. The fibres were impregnated with a bio-based epoxy polymer in order to produce completely green tensile testing specimens. The tensile properties of these plant-based composite materials were then evaluated. Overall, the fibres can enhance the tensile properties from the neat matrix, in the extreme case of PALF and hemp fibre composite, by more than double. The PALF and hemp composite shows a superior tensile modulus and strength to agave. This is because PALF and hemp fibre have a finer diameter than agave so they can be easily filled in the mould. In conclusion, the PALF and hemp fibre will be candidates for further fibre development for aerospace structural parts as they have good mechanical performance and high manufacturability.