 This was a key link in the US airmail network, connecting two important cities and regions with the transcontinental route through Chicago.Ten Carrier Pigeon biplane aircraft were built by Curtiss, one of Key's other business interests.These were used to open the NAT airmail service on 12 May 1926 on a route Chicago-Moline-St Joseph-Kansas City-Wichita-Ponca City-Oklahoma City-Dallas.