Thermal management on aircraft has been an important discipline for several decades. However, with the recent generations of high performance aircraft, thermal management has evolved more and more into a critical performance and capability constraint on the whole aircraft level. Fuel continues to be the most important heat sink on high performance aircraft, and consequently the requirements on thermal models of fuel systems are expanding. As the scope of modeling and simulation is widened in general, it is not meaningful to introduce a new isolated modeling and simulation capability. Instead, thermal models must be derived from existing model assets, and eventually enable integration across several physical domains. This paper describes such an integrated approach based on the Modelica Fuel System Library and the 3DExperience Platform. It combines 1D and 3D methodology and delivers capabilities normally limited to complex and time-consuming CFD computations at the speed and convenience of system simulations. The paper provides a description of the modeling library and puts thermal management in context with more general model-based design of aircraft fuel systems. The paper describes two aircraft fuel system models. A generic one including thermal aspects, and an industrial one at full complexity level. The former is described in detail, and the latter briefly. The objectives of this paper are 1. To suggest a modeling and simulation solution for aircraft fuel systems addressing the thermal challenges as thoroughly as all other key design drivers within a collaborative engineering platform, and 2. To apply the solution to an engineering problem, which exposes typical thermal constraints.