During peak months the airlines will jointly operate a total of 35 return services a week between Singapore and New Zealand, including Christchurch and Wellington flights.
Engine makers Rolls-Royce says some of the Trent 1000 engines in the airline's Boeing 787-9 fleet require maintenance sooner than previously indicated.
"Rolls-Royce does not have any replacement engines available while this maintenance work is undertaken which means some schedule changes are unavoidable", Air NZ adds.
The airlines will continue to operate one daily return service each on the Auckland-Singapore route, with a third service operated by Singapore Airlines during the Northern Winter season and Air New Zealand during the Northern Summer season.
While New Zealand's national carrier did not disclose the cause of the issue, the New Zealand Transport Accident Investigation Commission said it was investigating two events involving "engine abnormalities".
Air New Zealand will be making cancellations and rescheduling some global flights due to the incidents.
Said SIA's senior vice-president of marketing planning, Tan Kai Ping: "Our alliance with Air New Zealand has already benefited customers through more capacity, choice, improved connections and more codeshare destinations".
"Our investigation team is working closely with the airline, Civil Aviation Authority, engine-manufacturer Rolls Royce, and our colleague agencies in the United Kingdom and USA".
Both incidents involved the engines during climb on takeoff from Auckland, forcing them to turn back.
The issue stemmed from corrosion and cracking of turbine blades and forced Rolls-Royce to fit new blades on all the 787s operated by Japan's largest airline.