Flights with high thermal loads inside the cockpit can have a considerable impact on pilot physiological and psychological performance resulting in thermal discomfort, dehydration and fatigue. In this work, a Functional Mock-up Interface (FMI) based aircraft system simulator is utilized with intent to compute and predict thermal comfort. The simulator can for example serve pilots as a tool for heat stress and flight risk assessment, supporting their pre-flight planning or be used by engineers to design and optimize cooling efficiency during an early aircraft design phase. Furthermore, the presented simulator offers several advantages such as map based thermal comfort analysis for a complete flight envelop, time resolved mental performance prediction, and a flexible composability of the included models.