I went outside on my morning break. I walked out to the lagoon to stand in the sun. The sky was clear blue and the air crisp. Visibility was very good.When I first noticed the object I thought it might be a small cloud. But the more I observed it didn't appear to be. It slowly moved southbound along the Hwy 101 corridor.As it moved further away it started to disappear. When it totally vanished it immediately reappeared at a lower elevation and further away. When I finally lost sight of it, I estimate it traveled from Redwood City to Mountain View.