Till now, cargo operations are built on the backbone of older aircrafts that require relatively inexpensive modifications to haul pallets. The economics of the business rarely encourage brand new aircraft purchase with the exception of UPS and FedEx and ad-hoc specialized operators.
In the future, this might not be the case. In the era of fuel efficiency most passenger aircrafts were not designed to haul cargo. In-order to save on weight the main deck on the 777 was made of lightweight materials that is acceptable for passenger traffic. This in-turn makes it very expensive for cargo conversions.
In the future, this might not be the case. In the era of fuel efficiency most passenger aircrafts were not designed to haul cargo. In-order to save on weight the main deck on the 777 was made of lightweight materials that is acceptable for passenger traffic. This in-turn makes it very expensive for cargo conversions.