Are you planning to transmit the entire image from the DSLR in real time? I suspect the arduino just will not be able to handle that amount of data. Even if the arduino is fast enough, is your comm link fast enough to get the whole data flow fast enough to be able to be useful? My E-5 currently generates 4-7 megabytes per picture for JPG images, and RAW images are larger.
Depending on the DSLR, you have the problem of getting the image from the camera to the arduino for transmission.
I suspect instead of sending the whole image, what you want to do is run the DSLR in live view mode and use the video out feature of the camera to get a composite video stream out and still record the hi-def images on the camera's memory card. Then you would presumably use the normal means of sending video through your comm link (I assume sending composite video is already handled).
If it wasn't an airplane, you could use either Eyefi cards to transmit the images directly over wifi or the various wifi based solutions intended for car backup monitors, but I suspect the plane would be outside of the range of a normal wifi setup.