<p>Sustainable aviation fuels (SAF) can reduce aviation greenhouse gas emissions, yet their production scale-up to meet policy goals remains unexplored. Here, we describe the Global SAF Capacity Database to quantify global and European Union (EU) SAF capacity, comparing it to production capacity announcements. Despite announcements of 9.1 Mt year⁻¹ (2.2 Mt year⁻¹ in the EU) by 2024 and 38.9 Mt year⁻¹ (9.3 Mt year⁻¹ in the EU) by 2030, only 24% (26% in the EU) of the announced capacity was realized on time by 2024. Over 40% of the announced capacity for 2030 risks delays or cancellations. Using a diffusion model parametrized by announced capacity, realization rates, expected demand, and historical growth analogs, we calculate SAF potential scale-up to meet net-zero carbon emissions by 2050. Even if SAF follows the rapid scale-up of solar and wind energy, the global and EU capacity will fall short of respective targets by 42% and 18% in 2030, and 7% and 5% in 2050.</p>