over exposure

If the process suggested by Greg_S does not work for you, try this:

You will need a picture of a "good" sky. You can take it yourself, or obtain one via Google Images - look for Sky Pictures with Clouds. Then, proceed:

1. Open the picture with the ship. This will be the Background Layer.
2. Copy/paste the sky picture. It will come in on a separate layer above the background layer
3. Activate the move tool or the transform tool (CTR+T) and position the new sky picture over the old, blown-out sky.
4. Set the blending mode of the sky layer to Darken
5. Set your foreground color chip to white
6. Activate the Gradient tool, select the Foreground-to-Transparent, linear gradient and drag the gradient from below to the top of the ship's superstructure, while holding down the shift key
7. You may want to paint the horizon gently with a white, soft brush at reduced opacity so as to make it a tad lighter than the rest of the sky.

If you should elect to make a "Sky" yourself, a good light color is C7D7EA, good dark color is 628DC0.

There are many free cloud brushes which you can install on your computer and utilize for this purpose.

I would suggest using the File>Open in Camera Raw option.  This will bring up the Adobe Camera Raw editor, even if your file is not a raw file.  Assuming there is some detail available in the sky, you can bring it out by lowering the Highlights and Whites sliders and maybe increasing the Blacks/Shadows and Clarity.  You can also try out the other sliders to see if they work for your image.  Once you have completed your edits, click the Open Image button, then save the file in the normal way.

Here is a random photo with a sky lacking any detail.  You can see the added definition of the clouds when making the adjustments discussed above: