This photo was taken in 1919 and remains one of the most compelling photographic proofs of ghostly appearances. It is a reunion photo of a British Royal Flying Corps squadron who served together in the First World War. A face can clearly be seen lurking behind the fourth man from the left in the top row. (It has been magnified in the circle.) The face was easily recognized by the aviators as Freddy Jackson, a squadron buddy. The trouble was that Jackson, a mechanic, had been accidentally killed by an airplane propeller two days earlier! Jackson's funeral took place on the very day this photograph was taken.