The sky was masked, layer duplicated and blend set to multiply. Then the 2 layers were merged and adjustments to levels and color balance was done.
step 2 of 11
A gradient layer was layed down for the background. The aircraft was extracted with pen tool. The SR-71 was treated with adjustments to the levels and curves.
step 3 of 11
Some more clouds (taken from original sky source) added. Stars and comet along with vapor trail was painted in.
step 4 of 11
step 5 of 11
The planet was painted in CS5. I made a texture from this source.