Both Pan Am and Iran Air worked together with Boeing to push for the 747SP design, and Boeing had sought an attempt to compete with the DC-10 30 (up to a point).
The idea for The 747SP came from a joint request between Pan American World Airways and Iran Air who were looking for a high capacity airliner with enough range to cover Pan Am's New York-Middle Eastern routes and Iran Air's planned Tehran-New York route.
The Tehran-New York route when launched was the longest nonstop commercial flight in the world.
Iran Air had plans (before the 1979 Revolution) to launch 747SP services to SYD and LAX.
Both airlines took simultaneous deliveries and entered SP service in 1976.
The SP's were still being delivered with Upper Deck First Class lounges.
The 747SP had a much simpler single piece flap system, and these did not require the "canoe" fairings, rather than the immense and complex triple slotted Fowler flaps of the larger 747.
SAA SP's were soon to follow in service also in 1976, enabling them to now fly non-stop around the bulk of Africa, and Syrian Arab Airlines took a pair.
Braniff ordered a total of 4 747SP airframes but only actually took delivery of 3 of those.
Braniff suffered from high oil fuel prices, the economic recession, traffic downgrowth and withdrew from its Pacific routes.
As a result Braniff would withdraw the 747SP and the fleet was soon offered for sale.
One was quickly sold back to Boeing, one to Pan Am, and another sold on to Aerolineas Argentinas.
The 4th Braniff 747SP was NTU and eventually Boeing sold it to CAAC as N1301E.
Taiwan's China Airlines took 4.
CAAC would order 3.
Korean Air 2 (The last SP's delivered)
TWA and Qantas came a while later to the SP game in 1980/1981, and both airlines did not end up using their SP's on the dedicated routes as was originally envisaged.