Aircraft simulation software was used together to simulate a humanitarian variant of the MQ-9 Reaper drone as well as its longitudinal stability response upon dropping an aid payload. This project derives stability derivatives from the MQ-9 dimensions using the mass moments of inertia and approximate air- foil shape using Athena Vortex Lattice (AVL) code. The stability derivatives, aircraft properties, weights and control systems were modelled with Presagis FlightSim 14 to approximate the MQ-9 flight model. A graphics model was also built using Presagis Creator and the flight model and graphics model were unified into a virtual environment. Its longitudinal short period and phugoid responses as well as the lateral Dutch mode after dropping a 200 kg payload was recorded and analysed. The older Ryan Navion was also modelled using the same method which was used to model the MQ-9. The same dynamic responses were compared to real Navion flight test and calculated data in order to validate the aforementioned modelling method.