Aircraft are actually supposed to leak air. In non-bleedless aircraft, the engine compressors pressurize air to be used in the A/C unit, which then sends all the pressurized air throughout the cabin. To prevent excess pressure buildup, valves are opened partially most of the flight with a veinlike network of tubes venting air to the exterior of the aircraft.

Of course, if any damage occurred on the ground, this would be a non-issue entirely as the aircraft wouldn't be pressurized at all.