During the development of the Boeing 747SP, a combination passenger-cargo version called the SP Combi was proposed. With a large main deck cargo door in the aft fuselage, the SP Combi was billed as the ideal replacement for the aging fleet of Boeing 707 and Douglas DC-8 aircraft as it could fly 186 passengers and nearly 65,000 lbs of cargo farther and with better economics than a 707-320C with 147 passengers/6,800 lbs of cargo or a 707-320C freighter with 58,000 lbs of cargo.

The SP Combi's 328 seat all-passenger configuration could be quickly converted over to either a 242-passenger/four-pallet arrangement or a 186-passenger/eight-pallet arrangement. To test the idea, a China Airlines 747SP was used to test the accessibility of the main deck cargo door with standard main deck loading equipment given that the 747SP's wing trailing edge was much closer to the aft fuselage location of the proposed door than on the full size 747 Combi aircraft. Black tape was used to outline the door location and tests were successful. However, the airlines showed little interest and no SP Combis were produced.

Source: Boeing 747SP by Brian Baum, Great Airliners Series, Volume 3. World Transport Press, 1997, p41.

Contrary to popular belief, QANTAS did not order its two Boeing 747SPs for the long distance Los Angeles to Sydney route. Rather, the airline's orignal plan was to use them to connect Sydney to New Zealand's capital, Wellington- located on the southern tip of the North Island of the New Zealand, Wellington had a short runway that made operations by regular 747s impossible. In addition, the airport was frequently affected by erratic winds and poor weather. QANTAS's original intent was to use the 747SP's ability to operate on shorter runways to serve Wellington with more profitable payloads despite the operational limits placed by the airport authorities for safety reasons.

The first QANTAS 747SP entered service on 6 February 1981 as QANTAS Flight 55 Sydney to Wellington, but had to divert to Auckland due to poor weather at Wellington.

Only QANTAS captains were allowed to land the 747SP at Wellington as the first officer monitored the approach which was conducted at 125 knots to insure that the landing could be made using the markers painted on the runway. Landing too fast, too high, or too long, was a mandatory go-around.

It wasn't until 1984 that the airline's 747SPs were used on the Sydney to Los Angeles route.

Source: Airways, November 2008. "QANTAS Double Trouble!" by Mac af Uhr, p51.