Orange 1918 Curtiss Jenny Airmail 6 cent Scott #C1 plate block of six; number 9155. Quantity: 3,395,854.When US airmail service first began in 1918, it was a success, making more money than it spent. However, in the years that followed, it lost money because of increased costs due to a higher number of routes, greater distances traveled, and more mail that weighed down the planes. Mint, Full Gum, Previously Hinged.