The purpose of this paper is to present Thetis: a real-time multi-vehicles hybrid simulator for heterogeneous vehicles. This simulator allows Hardware In Loop (HIL) simulations including virtual sensors which allow to provide a representation of a virtual world, and including the support of communication devices. The architecture of this simulator is conceived so that it ensures a temporal decoupling between the virtual environment, the vehicles, sensors and communication simulators and, of course, the actual embedded controller which warrants us the temporal consistency of the results. Our contribution concerns the proposed simulator architecture. This architecture gathers all the important features required to simulate a flotilla (including communications skills). This paper presents the architecture and functionalities of Thetis and present some simulation results with the support of communications.