The Air Mail History of the Canal Zone and Panama, 1918-1941 (2 Volumes) by Capt. Julius Grigore, Jr. (2011)
Air mail history offers a great perspective into not just aviation’s past, but the geopolitics that shaped our world.
Volume I of II, available in hardcover, paperback and Kindle (2014). (**)
Volume II of II, available in hardcover.