Inspired by Caz Dalton's article "How to create simple in-flight digital photographs" I decided to have a go. However I didn't have room or much equipment, so I applied a bit of WW2 spirit and improvised.

General Description.
Step 1.
I selected the models I wanted to use and simply shot them with a Sony Cybershot 3.3
megapixel Digicam borrowed from work. I laid out a large sheet of matt white card, taping it at the front to the kitchen table and the wall behind so the card was swept up from the horizontal to the vertical. Lighting was pure daylight from the window.
I took many shots to choose from.

Step 2
Next I found suitable royalty free sky background images and brought them with the
selected plane shots together in Photoshop 6 on my Mac. I cut out the aircraft from the original background and adjusted brightness and contrast to suit.
Then I copied the cut out aircraft image on to the sky background on a separate layer.
Once this was done I adjusted anything that needed adjusting.  I don't build models with pilots or crew so I added them as necessary with the photoshop airbrush.

Plane by plane 
Huma 1/72nd Junkers EF128.
Once I had cut out the image and pasted it on to the sky background I copied the plane
layer twice and reduced them and adjusted the angles and colours.

PM 1/72nd Fw Ta183
With this one I wanted to try and give the impression of speed so I added some Motion
blur to the background in photoshop.

Planet 1/72nd Messerschmitt Me P1110/1
Similar process to the Ju EF128. The main image layer was copied and the angle and size adjusted.
Peter