Launched in 2016, the "Capital Express" service from Wellington to Canberra and on to Singapore has been ditched in favour of flying to Singapore via Melbourne.

After sixteen months, Singapore Airlines has ditched its experimental "capital express route", opting to reroute its Wellington flights through Melbourne.

From the end of April, the airline will fly Boeing 777-200 four times a week from Wellington to Singapore through Australia's second largest city, replacing the existing service through Canberra.

While the Canberra service was launched with fanfare, prompting a sister city agreement between the two capitals, news of the change to Melbourne was quickly welcomed, prompting predictions of price cuts.

STUFF One of the "Singapore girls" is greeted on the tarmac when the inaugural Singapore Airlines flight to Wellington landed in 2016.

"With all due respect to Canberra, I think there'll be more people from the lower North Island and upper South Island, both from a business and a holiday point of view," House of Travel's commercial planning director Brent Thomas said.

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Air New Zealand flies between Wellington and Melbourne six times a week for most of the year, while Qantas flies the route daily. The wide-bodied Singapore Airlines flights would add around a third to the capacity on the route.

While Thomas said New Zealanders were poised to travel overseas in record numbers in 2018, he expected Singapore Airlines' competitors would respond with lower prices.

"There is likely to be some sort of response from those who compete against it on that route."

The flights via Melbourne will now land in Singapore at around 11pm, instead of the current 7am, which would appear to be less convenient for most travellers. Singapore Airlines denied this.

Singapore Airlines' introduction to Wellington comes at a cost to ratepayers, after Wellington City Council chief executive Kevin Lavery approved a multi-million dollar agreement to provide "marketing support" for up to a decade.

The terms of the agreement have never been released, but mayor Justin Lester confirmed the agreement was for the airline to fly through any Australian city, meaning the support would continue to be available.

Information requests on the subsidy agreement have yielded little documentation, and the Taxpayers Union has launched a petition calling for the payments to be ended.

Since the service was launched, Lester has talked up the possibility of the service being increased to a daily one, which he said was more likely under the new configuration.

"It gives us greater opportunity to increase it to a daily flight services in the near future, or in the future."

Lester said the change would not impact the sister city agreement with Canberra, adding that he hoped one day there would be another direct flight between the two cities.

Singapore Airlines' explanation of the change was that it was designed to provide more seats between Wellington and Singapore, which were often unavailable because of demand from Canberra to Singapore.

"After 16 months of operation it's quite clear that Wellington has performed very well for us ... The question was how do we grow the operations from here," Singapore Airlines New Zealand general manager Simon Turcotte said, prompting the move through Melbourne.

While demand between Wellington and Canberra was limited - at times the flights were so empty that passengers were required to change seats to ensure weight was evenly balanced on take-off - demand was apparently strong between both cities and Singapore, meaning some flights were sold out between Canberra and Singapore.

Turcotte said the move would mean there were more flights available to sell to Wellingtonians.

"It's to provide more availability to the Wellington market to sell to Singapore and beyond and the reason for this is that because Melbourne already has four other flights a day [to Singapore] we can offer those extra seats to Wellington without impeding the Melbourne market."

Tagging the flights to Melbourne offered "more support in the softer months".

Wellington Airport welcomed the move.

"The Singapore service has been near capacity onwards from Canberra over the busy summer season, and we recognise the need to develop the long-haul service for both the Wellington and Canberra markets", chief executive Steve Sanderson said in a statement.

Once Singapore Airlines establishes operations, it tends to stick around, even in difficult circumstances.

Operating continuously to Auckland and Christchurch for decades, the airline maintained the frequency of its services to the South Island's largest city following the devastating 2011 earthquake.

In 2015 Peter Townsend, then the chief executive of the Canterbury Employers' Chamber of Commerce described the airline as "extremely loyal" to the city.