AWB on K7

I am having problems with Auto White Balance on my K7, but only on particular shots. Generally it is spot on, coping with tungsten, sun, shade, night shots etc. However, all the aerial pictures I take seem to be an average of 1500K out, on the cool side, ie it takes them at 5000K and I have to adjust it afterwards to between 6500 to 6800K. Anyone any idea why it is doing this? I have been wondering if it has trouble coping with the colour blue. Is there some way of calibrating the camera each time I take pictures, as the discrepancy is not consistent? I had an Olympus E520 which was always spot on with aerial shots.

Any input appreciated.

Atmospheric haze plus subdued ground colors due to distance plus high UV content can play havoc with AWB.