The aeronautics community needs several alternative methods and tools to describe and analyze interactions between human operators and systems, according to some constraints (e.g., human factors, air safety, etc.). Hence, it needs to build models from the observation of real interactions, especially piloting, and to use extant theories from several fields: cognitive ergonomics and artificial intelligence, mainly. S-ETHOS sketches out a knowledge-based system that analyzes human pilot activities and provides feedback to improve air safety by giving measured appraisal of pilot error. The core of S-ETHOS is the ETHOS model that depicts the standard behavior based on the human pilot. S-ETHOS helps any air safety expert to simulate the pilot behavior during his mission and then will compare behavior between the simulation and real situations. It allows the air safety expert to know how the pilot assesses each situation. We implemented the ETHOS model according to an object-oriented approach, relying on a knowledge modeling language called OBJLOG II+. This model provides a first keystone to understanding how the human pilot captures and builds his environment through complex states. We will discuss the identified behaviors and potential deviations and associated situations.