Very large dark rectangular object silently tracking across sky was seen on two seperate occasions

As a 17-year-old amateur astronomy enthusiast, many years ago, I witnessed the same very large and very dark rectangular object silently tracking across the sky from NNW to SSE on two occasions about one week apart from one another.  Object was initially spotted near zenith on both occasions.  Object appeared to move at roughly 2 times low earth orbiting satellite speed.  Size was approximately 1 by 2 degrees or 2 x 4 moon diameters.  Direction of movement was parallel to its long dimension.  Seen with naked eye only.  
On both occasions I quickly ran into house to retrieve binoculars but object was lost in trees or disappeared.   I called to my father on the second occasion but he was not able to come outside in time to see it.