How passenger planes are given a second life as cargo jets

Demand to convert retired passenger planes into cargo haulers has surged, a lucrative trend that allows these older jets to serve a new mission: transporting goods ranging from produce to pharmaceuticals worldwide. Cargo rates have eased from record highs, but demand remains high with conversion slots sold out for several years. Converting some larger aircraft can cost more than $30 million. CNBC gets an inside look at what it takes to turn a passenger plane into a freighter.