The principle behind these cards, called lenticular photography, is essentially an illustration bearing two superimposed views of the same image taken from slightly different angles, on a transparent mount striped with a multitude of imperceptible parallel strips (Xograph process). On account of these strips, each eye, looking at the print from a different angle, sees only one image. Thee three-dimensional illusion is produced when this binocular vision is interpreted by the brain. 3D airplane postcards has been printed under the brand of XOGRAPH, as far as I know held by Eastman Kodak, and TOPPAN a japanese Company. What killed these style of airline postcards was the enormeous price of production, so unfortunately 3D airline postcards has never been succeeded. A more recent attempt to bring an three dimentional impression to the viewer is to use 3D-glasses instead of the costly transparent XOGRAPH-stripe. The disadvantage of this technique is that the phtographs does not show a real color picture, because a two coloured, mostly green-red picture is needed to bring out the three dimensional effect by using the 3D glasses.