Here’s a film about the age of “flying boat” air service, The Flying Boats.
Air mail service provided the entry point to develop the infrastructure that set the stage for the development of commercial passenger service.
The Lake Union Virtual Museum project has a video that describes the development of the Alaska bush plane service from the pilots who flew Boeing’s seaplane airmail service to Alaska (and who were rumored to add undocumented stops in Victoria, BC to pick up alcohol during Prohibition). Again, air mail came ahead of passenger service.
Note that the innovation that’s implicit in the development of airplanes capable of providing commercial passenger service across the Atlantic Ocean does not appear to depend on federally funded “research”–or, if such research is somehow involved, Pan Am did not have to negotiate patent licenses from a bunch of universities to obtain what it needed. Rather, there was a robust public domain of science and engineering.