Saucer sighting in 1970s near Phoenix, AZ.

Sometime in the mid-70s, I was driving from Williams AFB toward Apache Junction.  The day was clear and cloudless.  I saw a saucer-shaped object rise out of the desert in front of me and slowly ascend into the air, straight up, until it was out of sight.
At the time, I tried to guess the size of the object and estimated that it was at least as large as a high school football stadium.  It was a dull silver color and looked like the flying saucers in old sci-fi movies.  There was absolutely no sound associated with this sighting.
I thought I would see something about this in the newspaper, but did not.  I was so astounded by what I saw and thought surely someone else would report it, as I could not possibly have been the only one to see it.  I did not tell anyone for years, thinking people would think I was a nut.