Not a screener but happy to provide a bit of input:
Motive is kind of a catch-all rejection reason that the screeners will use when the composition or theme of the picture isn't consistent with what the site wants to see. A common motive rejection is pilots waving at the photographer. In your case I honestly don't dislike the motive; I think the sky is interesting as well as the angle. The crop is probably most important here, and they're probably looking for a wider picture that includes more of the instrument panel. A more head-on shot might also have been received better than this high-and-to-the-side perspective (maybe that's the main motive rejection).
The lower instrument panel is certainly dark, and I think some editing software should be able to elevate that a bit.
These two pictures seem most comparable to yours as far as the natural lighting. The 777 picture is definitely brightened, but you can see both have more head-on angles than does yours.