Real Famous WWI Ghost Airman Picture

Taken in 1919, this ghost photo of a RAF (Royal Air Force) squadron from World War One has an extra ghostly face in the picture. It is believed to be airman,Freddy Jackson, an plane mechanic who had been accidentally killed by an airplane propellor two days before this photograph was taken. His funeral is said to have taken place the day this photograph was shot. Members of his air squadron identified his face, right away, believing Freddy must have showed up for the now, haunted picture, unaware his body had expired. Freddy's ghostly apparition appears behind the airman in the top row, fourth from the left.

We enhanced the ghost airman's face to see him more clearly. It looks like the right side of his chin is fading out. Is this proof of an apparition or just a double exposure created by the photographer to get Freddy in the pic?