Aerodynamic breakup (aerobreakup) consist on the decomposition of liquid bulks into smaller droplets due to the effect of a gas stream. Depending on the flow parameters, a liquid drop affected by a gas stream can evolve in several aerobreakup modes [1, 2]. In particular, bag mode breakup takes place at moderate to low gas Weber numbers. During this process, the drops deforms into a film with a bag shape. As the bag radius increases, the film thickness decreases until a hole forms and expands, bursting the bag into a spray. This mechanism is present in several breakup scenarios and it is of great interest to understand the underlying physics of liquid atomization. In this work, we present numerical simulations of a single droplet submerged in a stream with sets of parameters corresponding to bag mode breakup regime. We solve Navier-Stokes equations for the two-phase flow using a Volume of Fluid (VOF) method with a Piecewise Linear Interface Capturing (PLIC) and geometrical advection schemes on the volume fraction and momentum equations. We also apply Adaptive Mesh Re- finement (AMR) to reduce the computational cost, using high mesh resolution only in the region of interest. These tools are programmed in the Basilisk open-source suite (http://basilisk.fr/)[3]. The deformation of the drop into a film and the posterior evolu- tion of its thickness is studied until the formation of a hole.