Some small South Pacific airlines such as Air Nauru and Solomons operate sole 737s. Often these planes are painted in the livery of the South Pacific operator but are actually owned and maintained by airlines such as Qantas.
Solomons Airlines 733 flies with QF during the week and for Solomons on the weekend. The plane carries Australian registration. Ansett had a similar arrangement with Polynesian Airlines for a long time.