Flight simulators are widely used in aerospace industry for multiple purposes. This paper highlights the importance of engineering flight simulators and presents a 3 degrees-of-freedom longitudinal flight simulation model that can be adopted to simulate aircraft behaviour for engineering analysis. A brief overview of aircraft design process is presented with reference to flight simulation procedure. A special emphasis is placed on Massachusetts Institute of Technology's Athena Vortex Lattice program that can be used to calculate aerodynamic characteristics for a given geometric configuration. The paper explains modeling of aerodynamics and thrust blocks and shows how they can be linked with equations of motion block to build a comprehensive flight simulation model. Matlab script that linearizes and trims equations of motion is also discussed and key stability results are explained in detail. Simulation test cases are also presented. Several recommendations are made at the end of the paper on the potential use of simulators and also on ways of improving the simulation model.