I came across this photo of a World War I dogfight and wondered about the different airplanes used in that war. After a quick search, I found some scanned photos of a The Chicago Daily News War Book describing the different World War I airplanes. In the above photo the planes with the circles are Allied (perhaps English?) Morane planes while those baring a “+” are German Fokker planes. (I’m basing this off of a comparison with the photos below, so if you think I’m wrong please let me know!)
The Chicago Daily News War Book for American Soldiers, Sailors and Marines, Copyrighted 1918 by The Chicago Daily News Company. Chicago, IL; page 45- 50. Found online here.