pulsing silver object in the daytime

I live about 15 miles from O'Hare and have lived there all my life.  
One day in the summer of either '94 or '95 I saw a craft from my window(as I was on the phone with a fiend) on the North side of the house.  Basically, this craft appeared during the daytime and was travelling N-NE at a high altitude.  It was definitely travelling above the normal flight path of the incoming planes which usually come in the E-W directions at a few thousand feet.  
This craft flew over at a constant speed and looked spherical in shape, I say this because the reason it caught my eye when I was talking to my friend on the phone was that it was glaring like a silver object reflecting the sun.  I have seen planes glare the sun before, but this was not a plane because it was pulsing this glare.  
In other words, it travelled across my window and pulsed a silver glare as it flew straight across the sky.  I kept asking my friend who lived about 2 miles away if he could see it relative to my point of view but he didn't see it... it was very high up(maybe ~20 thousand feet) or it was just closer and small, but it was only in my view for about one minute. 
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