Supersonic combustion ramjet (SCRJ) engine research and development, begun some 40 years ago, is the key to airbreathing hypersonic flight. Many unexpected complexities of SCRJ engine combustion and combustor-inlet interaction have been continuing challenges. However, valuable progress has been made in several aspects. In the next few years, it would appear that significant flight testing will take place in several countries and this should lead to further understanding of SCRJ processes in engine design for cruise and accelerator vehicle applications.