Replace the sky, paint some clouds and add some light effects using overlays.
step 2 of 4
Place the sources and paint over them to make them fit better into the scenery, some shadows are needed too
Make some shapes with the pentool and paint and add some gradients to make some light effects in color dodge to make the bubbles.
Add the aperture mechanism and blend it
step 3 of 4
The aircrafts were rendered in poser
step 4 of 4
Place the aircrafts, add lights from the turbines, and the vapour trails.
Add some light effects and finished.