The U.S. Army just launched its Long Endurance Multi-Intelligence Vehicle (“LEMV”).  This hybrid blimp and airfoil is over a football (U.S. football) field long and is over seven stories high.  The blimp will use a combination of lift from helium gas, which is non-flammable, and its airfoil design.  The long endurance of the vehicle will make it ideal for surveillance of large areas during its 21 day mission cycle.  In addition, it will serve as a cargo and supply  vehicle.  Read about it here.
So, if you look up in the sky tonight and think you see the mother ship; do not fear, it is simply the U.S. Army on patrol.