Ah, nice pics! The D70 is pretty nice, what lens did you use for these shots?
A few things I see, first you mention that default settings were used. This appears to show in the pics, you'll notice that in the shots where you were panning with the landing there is a slight loss of sharpness, while in the taxi pic things are very sharp. In this situation the camera program probably had chosen a slightly slow shutter speed. To solve this, open the lens further (if it's fast enough) and raise the shutter speed.
Second, on very cloudy gray days, you might get an interesting result if you slightly warm the tone of the images to over come the strong blues from the sky. I would suggest doing this in the PC, not in the camera, just so you've got a clean base image to work with in any case.
Here's an attached warmed version.
Linear Mode
