Today, aircraft are protected by strong safety properties, qualified operators and process-based security measures. However, considering the recent evolution of in-flight services towards more connectivity, resource sharing and advanced entertainment functionalities, together with the increase of threats targeting embedded systems, the potential malicious modification of an aircraft application must be seriously considered for future systems. In this context, several solutions can be developed to improve aircraft security. In particular, Host-based Intrusion Detection Systems (HIDS) are relevant to deal with targeted threats such as an insider attack. This paper presents the specific constraints of building an HIDS onboard an aircraft, and discusses some relevant solutions that satisfy these constraints. These solutions are evaluated in terms of detection efficiency and resource consumption in order to select the solution that allows the best trade-off between efficiency and performances. The implementation of this solution on an embedded avionic computer is also described.