Fault injection, an estimation method based on experiments and an important component of integrated vehicle health management, plays an important role in vehicle safety. This paper describes the principle of fault injection. Several methods of fault injection and their applications in aircraft are reviewed in detail. Emphasis is put on the analysis of the pivotal technique used and the technical difficulties faced when fault injection technique is applied to structural, thermal-protection, hydraulic and mechanical systems of vehicle. A prospect in this field is described at the end.