Contrast problems!

So every aviation picture I've taken lately has had way too much contrast. It's happened with five different lenses (70-300 IS, two 100-400s, 300 f/4, and 50 f/1.8), and it doesn't happen with anything else I take pictures of.

One from a couple of weeks ago that got rejected from JP for too much contrast (all 600 or so shots from that afternoon had similar histograms):
http://farm3.static.flickr.com/2009/...c3163c.jpg?v=0

Two from yesterday that I suspect will be rejected for the same reason:

http://farm3.static.flickr.com/2233/...a53df5.jpg?v=0
http://farm3.static.flickr.com/2343/...de5855.jpg?v=0

The two from yesterday, I reduced the contrast to -20 in Camera Raw. It helped a bit, but not enough; the sky is still a very deep blue, while the airplane looks fine. I'm shooting in Aperture Priority mode, between f/9 and f/11, with +1/3EV bias, at ISO 100, on a Canon 20D. Does anyone know what to do about this?