A blue, oval shaped craft with glowing panels through the center flying in odd patterns and hovering around the area.

It was 1975 in Bourbonnais/Bradley IL. I was 10 years old and lived in Stadium Heights apartments when  someone had noticed a strange, blue, oval shaped craft with glowing panels of different shades of blue through the center flying in odd  patterns and then hovering around the area . This was broad daylight.
Soon, a crowd formed and the police were called. They responded and just stood and watched  like everyone else. The ship would hover, fly quickly  towards us and then  turn and fly off in another direction just to stop and hover once more in a different position than when it started. At one point, an officer grew alarmed and ducked down behind his squad car door with his weapon drawn because the craft had turned in our direction and came closer than before.
I had lived at the opposite end of the complex from where the crowd was gathered and walked back to our apartment to get a drink of water.  As I was returning , the ship flew over the area where I was walking and I got a close look at it.  It stunned me when it came down lower because it was so big that it looked as though it might crash into the nearest building.  It hovered a minute and then went back to the general area that we saw it in originally.
After about 40 minutes or so it turned and flew off as quickly as it appeared. We were told by the local police that it was a new advertising machine for the bank.  Can you imagine that?  It flew, there were no wings and it had no words on it.  That was a totally impossible scenario.
Witness indicates that the date of the sighting is approximate.  PD