In late August, this mysterious white schoolbus was sighted in an open space parking lot in the Sandia mountain foothills of Albuquerque. The windows were darkened and the vehicle had U.S. Government plates.
This bus was empty at the time it was photographed, but 20 minutes later it was observed driving through a nearby suburban neighborhood. While most of the windows were shut (and darkened), a few opened windows revealed that the bus was filled with military types.
A similar white bus is commonly seen entering Groom Lake/Area 51 in Nevada as noted in the image below from an MSNBC/SyFy documentary about secret military facilities.