Boeing's latest commercial market outlook forecasts a doubling of the global freighter fleet from 1,760 to 3,500 aircraft in the next 20 years.
This increase will include 970 new-build freighters and another 1,990 converted passenger airframes.
Much of the new-build total - some 690 aircraft - will be made up of large-capacity freighters, with payload capability above 80t.
The other 280 new-build freighters will be in the 40-80t sector, but Boeing sees no demand for new freighters below this size.
Instead the freighter demand in this lower segment will be met by the conversion of 1,240 narrowbody aircraft.
The new-build freighter market will be worth $250 billion, with large-capacity freighters representing 80% of this value.
Boeing said that average air cargo traffic growth would reach 5.6% over the next 20 years.