This talk will show how Software-In-The-Loop(SITL) simulation can be utilized in the ROS environment to be able to simulate the full workflow of a real vehicle. After a brief introduction of the overall architecture of the simulation toolchain, we discuss how to test your own vehicle as part of the simulated environment. Since the PX4 Firmware is directly run inside the simulation environment, a transition from a simulated vehicle to a real system can be done in a safe and seamless manner. Also, we introduce a new simulation environment using an advanced flight dynamics model using JSBSim.