Regarding the quality, I would have to agree here with the screeners decision. Not that the overall quality of the picture is bad but rather that something went wrong during the editing process.
I think your picture is slightly soft/blurry/out of focus (front landing gear, wings, windows,etc), and at the same time there are some parts oversharpen (titles, flag, reg). All this indicates to me that you tried to compensate the soft look with a tad too much sharpening. Additionally, the contrast is a little off (compare areas in light with the ones in the shadow, does not look right), and maybe you even applied some brightness adjustment. In this case, all this would also explain the 'artifacts' or JPEG compression issues that has already been hinted to (they come from playing too much around with brightness/contrst/sharpening, so it's not really a JPG compression issue).
I hope this comments help you when you reedit this one, which I sincerely hope you'll do since it is a very nice one!
[Edited 2007-02-05 15:49:41]
Just sit back, relax and have a glass of Merlot...enjoy your life!