You may not use ANY editing tool to move, remove or duplicate any element of your photograph that would change a typical viewer's description of the photograph (aside from color), even if the tool is otherwise legal, and regardless of whether you intended the change when the photograph was taken.
Since this is a bird in flight I'll assume the sky was virtually white to start with and very little editing has been done. In which case this is an excellent shot that meets the challenge well.
Even though this is a good shot I feel that the subject is too alienated from the background as there is nothing to put it in it's natural suroundings.