Prior to the arrival of widebody jets, with their voluminous underfloor belly cargo holds, it was not uncommon for the major US trunk airlines to operate fleets of freighters. The postwar air freight market had never really grown in the way that had been forecast, however the limited cargo capability of passenger prop-liners and the relative lack of reliability of piston engines meant that there was a need for pure freighters, if only to ferry engines to stricken fleetmates.
By 1961 the variant was known as the DC-8CF, though for marketing purposes it was to be known as the ‘DC-8F Jet Trader’. Permission for a prototype was given in May 1961 but by now the design had evolved further losing the swing-tail (to save weight). The aft pressure bulkhead was moved further aft increasing all passenger capacity to 189 and the passenger/cargo divider became a moveable bulkhead with up to 11 different internal configurations. Two extra emergency exits were added aft of the wing and seats and forward toilets were palletized for easy removal. There was a selection of various other structural strengthenings in the floor and undercarriage to support the increased weights.
Three versions of the JT were offered for sale – the combi with a maximum payload of 91,000 Ibs, all passenger (50,000Ibs) and all cargo (96,000Ibs). The all cargo variant was unofficially known as the DC-8-54AF however Douglas itself referred to both the freighters and combis as DC-8-54JTs. The Jet Trader variants re-energised the DC-8’s sales over the next few years with airlines like JAL, Garuda, KLM, SAS and VIASA acquiring all passenger versions. The combi version was popular with airlines like Trans-Canada (later Air Canada) and in particular with supplemental carriers like Trans International.