It's a very nice photo, however I see a few things which may have warranted the badquality rejection. Firstly, the aircraft looks oversharpend in places - try resharpening and using a selective sharpening technique. Second, it has a pasty Neat-Image appearance in places - did you use any Neat-Image? If so, try re-editing without N.I. And finally, there is still some noticeable Jpeg compression.
I would recommend a complete re-edit, taking into account the items I mentioned previously and making sure to save at the highest quality/lowest compression setting.
You may also want to consider lightening the photo a bit, too.