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.