Have spotted this aircraft flying over the western U.S. more than once this July: a couple of times in early July north of Spokane, WA, and today over the Silicon Valley area. All times it was flying very low, but was relatively quiet for how close to the ground it was. It appears to have two propellers on each wing and is a plain gray, which makes me think it may be military. My searches for military aircraft that fit this description have come up blank though. Any help with identification is appreciated!
Blurry photo below is the best I was able to get.