Controller development of aerial vehicles is a long-standing task during aircraft design and has a large impact on the resulting systems performance. In today's integrated design loops, ideally all components of the aircraft must be considered in simulation and testing in order to develop complex system architectures and meet performance requirements. One of the tools that are suited for modeling and simulation of a multidisciplinary aircraft and systems assembly is DLR's FlightDynamics Library, which takes advantage of the capabilities of the Modelica modeling language. In this work, a new augmentation to the library is discussed, which implements a range of common aircraft control concepts which can be used for design of new controllers, closed-loop simulation and experimental testing via code-export. The library is set up in a modular way, so that flight guidance and flight control systems can be developed for multiple aerial platforms, including manned/unmanned fixed- and rotary-wing aircraft. For this paper, a simulation example is provided by means of an autoland controller that shall be designed for a high-fidelity 6-DoF fixed-wing aircraft model in Modelica. The combination of aircraft and controller models is subjected to a three step synthesis process, which yields a controller that is robust against external and internal disturbances.