In April 2018, Boeing announced its investment in Reaction Engines, through Boeing HorizonX Ventures with a $37.3 million Series B funding alongside Rolls-Royce PLC. Rolls-Royce and REL announced a strategic partnership in August 2020, with a £20m investment.
In January 2023 the company announced that it had raised a further £40m from backers including the United Arab Emirates Strategic Development Fund.