U.F.O. sighting was astronomic in size as to blot out the sky on all horizons.

The U.F.O. was enormous in size as to blot out the sky in every direction.The  ufo in question was gray/silver in color, the bottom side of the craft seemed to be flat closest to the ground, and seemed to bevel upwards towards the ends ... even though you could not see the end of the craft because of its size. It had little lights on its underside in colors of Red, Amber,White, Blue/purple. I remember bolts of electric current bouncing of the bottom arching at will. It was enough of a sighting that the U.S.A.F.[Westover Air Force Base/Chicopee,MA.] arivved on the scene not less than twenty mins. after the sighting. A Captain and Lieutenant or Major.
Date is approximate.  PD