Bird strikes are a major risk to an aircraft especially during the take-off and landing stages. It may result in significant loss of human life and property damages worth millions annually in the US alone. This research is aimed at development of a computer-based modelling and analysis of a large 8-lb bird on an aircraft engine, and comparing the results with those from impact analysis of a smaller 4-lb bird. As the current Federal Aviation Regulation (FAR) are based on the utilization of smaller 4-lb bird only, this research helps in examining whether the use of s small bird is appropriate, or consideration should also be given to larger bird impact testing. In this study, the Smooth Particle Hydrodynamics (SPH) technique is used to model the 4-lb bird. This model is validated by simulating its impact it on different aluminium plates. Various parameters such as deformation, Von Misses stresses, forces and impulse are recorded and compared with the experimental values. Similarly, the large 8-lb bird model is created, and it is numerically impacted on the same metal plate, and the results are compared with the ones from small 4-lb bird impact model. Detailed geometry on an aircraft jet engine is then modelled in CATIA V5, while meshing is done in the Hypermesh. The bird models (4-lb and 8-lb) are impacted on the rotor blades of an aircraft engine using the LS-Dyna, according to the FAR 33.76 regulation. Results obtained in these simulations are compared, and failure damage of the engine is quantified. The study shows that damage caused by a large 8-lb bird model could be significantly larger than that of a smaller 4-lb bird model. Thus, this study proposes that the use of large 8-lb should be considered in FAR regulations for aircraft components including engine certifications.