The company's Synergetic Air Breathing Rocket Engine (SABRE), with its regenerative cooling system that could protect a hypersonic jet engine by instantly cooling the incoming air using liquid hydrogen, attracted investors such as BAE Systems, which purchased 20% of Reaction Engines stock in 2015, and led to funds coming from Boeing, Rolls-Royce, and others.

However, this year, the company found itself in major financial difficulties due to unexpectedly slow growth and the inability to secure an additional £150 million (US$193 million) in funding, followed by BAE Systems and Rolls-Royce being unwilling to put up bail-out capital.