Transportation: This Strip Is Necessary

Before long, disembarking jet passengers may be surprised to see workmen behind them busily carting off the whole insides—seats, galley, cabin partitions—of their aircraft. In Seattle last week, United Air Lines showed off the plane that can do the strip: the 600-m.p.h. Boeing 727 QC (for Quick Change), first airliner designed to moonlight as a cargo plane after turning in a full day, and fat profits, as a passenger carrier.

Because airlines needed a medium-haul plane that could keep on earning after prime daytime passenger hours, United helped Boeing jigger its tri-jet 727 to set the entire cabin area on...