Three-dimensional symmetric computational fluid dynamics (CFD) simulations are performed to study the deformation and breakup of water drops in an air stream at different Weber numbers. The types of drop breakup considered lie in the bag breakup, the stamen breakup, and the sheet-thinning/stripping breakup regimes. Symmetry conditions are assumed so that only one-quarter of a drop is simulated. A fully three-dimensional simulation is first conducted to justify this symmetry assumption which is then used in the remaining CFD simulations. In order to keep the drop within the fixed computational domain, the shifted Eulerian adaption (SEA) method has been developed. In this method all the field values are shifted back by one mesh cell after the center of the liquid mass has moved forward by one cell, while at the same time the boundary conditions are maintained. The CFD results reflect the behavior of the different breakup regimes observed in experiments. Further, the drop size distributions of each breakup regime obtained in the simulations are quantified by lognormal distributions. These product drop size distributions are consistent with the experimental observations and agree with simulation results reported in the literature. Furthermore, the dimensionless breakup times are in acceptable agreement with experimental values.