Core of the work is an engineering oriented modeling approach of human cognition and of interaction using a specified situation-operator (SO) scheme. The strong relation between human interaction and mental models can be shown as well as the connection to related mental representations. The SO-scheme allows modeling of differend kinds of systems resp. modeling approaches, e.g. hybrid systems. The SO-scheme gives the framework modeling human activities and related mental activities including mental representations of models. The ability of the approach is demonstrated analyzing the crew-communication of the Birgenair aircraft accident.