Willow Runs Learfraktare under det glada 70-talet
During law school I had hauled freight out of Willow Run in piston twins. About the time I graduated and began studying for the Bar exam, a number of the operators which had been flying Beech 18s discovered that the per-mile operating cost of a well-used Lear 23 or early 24 was about the same as the Beech, and the Lear got the freight delivered much, much faster.
Suddenly there were Learjets at Willow Run, almost all of which were being operated by folks who had previously done nothing but run single-pilot airplanes.
They weren't exactly sure what to do about the requirement of a copilot in a Learjet. The regs said that the copilot had to go through some training and make three takeoffs and landings in the airplane. However, there simply wasn't the money for any training, or to pay more than a pittance for a right seat warmer and, by gawd, the Learjet 23 panel was set up for single-pilot operation anyhow, even if Lear couldn't convince the FAA to grant single-pilot certification.