Singapore Airlines general manager New Zealand, Simon Turcotte said the decision to operate the new plane to Christchurch reinforced the airline's commitment to Christchurch and the South Island.
Singapore Airlines first touched down at Christchurch International Airport in 1986, the first international long-haul carrier to fly to the Garden City.
"The introduction of Premium Economy will make Singapore Airlines the only long-haul carrier offering the cabin daily out of Christchurch on a year-round basis," he said.
The A350-900 has 253 seats, 13 fewer than the 777-200. The new plane has three classes, 42 seats in Business Class, 24 in Premium Economy Class and 187 in Economy Class.
The flight will continue to operate as part of Singapore Airlines' and Air New Zealand's alliance partnership, with Air New Zealand codesharing on the service.
The A350-900 provides customers travelling to and from Christchurch with features such as higher ceilings, larger windows, an extra-wide body delivering more space and comfort as well as lighting designed to reduce jetlag.
Aircraft such as the A350 and Boeing 787 Dreamliner are up to 20 per cent more efficient than the aircraft they replace because they are lighter, have more modern engines and aerodynamics. These new generation planes make up more than 20 per cent of capacity flying to and from New Zealand.
Singapore Airlines has 67 A350-900 aircraft on firm order and have already taken delivery of 21 since the first aircraft entered the fleet in March 2016. It will use an ultra-long-range version of the plane on the Singapore-New York route later this year, which will overtake Qatar Airways' Auckland-Doha service as the longest in the world.