Thanks, Lili, HiredArm, and Will.
I didn't use a polarized filter, though I might try that. The third one was on a flight from Friday, and I remember the window had two panes of glass (or plastic?) that were scratched. Other factors might be the relative level of pollution and the angle of light (early morning and late afternoon seem best for 3-D-like shadows). For whatever reason (probably all of the above), the resulting files differed in the amount of detail and contrast I could pull from them.
To illustrate how much post production can draw from an image that has the right elements, here is a straight RAW-to-JPG transfer of that first image. Then that same image after going through SPP. Then that same image after more image enhancements within Lightroom. I tried to do the same with the other two shots but wasn't able to do as much with them.
This might also be of interest. It's a heavily processed window shot taken with another camera (a Leica M8.2). I'm not sure if the gray blobs are from the window or the camera sensor. More of a work-in-progress. The unprocessed version follows it.