SINGAPORE - The Government is still looking for the most optimal way to pay for Changi Airport's Terminal 5, and does not rule out other funding methods, said Senior Minister of State for Finance Indranee Rajah on Tuesday (Feb 6).

She was responding to Workers' Party MP Pritam Singh (Aljunied GRC), who asked for the Finance Ministry's position on the International Air Transport Association's (IATA) stand that major airport expansion works should not be pre-funded through taxes on travellers.

The Straits Times reported last month that passengers flying out of Changi may have to pay an additional $10 to $15 in fees, to fund T5 and other works in Changi East. Transit passengers could be charged half this amount.

On Monday, IATA's chief executive officer and director-general Alexandre de Juniac voiced opposition to these plans.

"We have mentioned many times that we are not in favour of pre-funding. We have a permanent dialogue with Singapore on this and we will keep reiterating and repeating this," Mr de Juniac told reporters at an event here.

On Tuesday, Ms Indranee told the House: "We don't rule out different ways of funding but we are sort of not committed to a single model.

"We will try and find the most optimal way to do the funding and spread it out over the proper period of time," she added.

Ms Indranee also detailed how the Government manages and reviews large-scale infrastructure projects like the Tuas mega port, in response to Mr Henry Kwek (Nee Soon GRC) and Ms Sun Xueling (Pasir Ris-Punggol GRC).

Projects that exceed $100 million, which make up more than two-thirds of Singapore's infrastructure spending, will be scrutinised by the ministry in charge as well as MOF before it can proceed, she said.

A Development Planning Committee (DPC) comprising three Cabinet Ministers must give the final approval.

Projects that cost more than $500 million are put through a "gateway process" and have to be reviewed by an advisory panel of public officers, academics and industry practitioners.

The review looks at the strategic business case of the project and its design. These large projects must also be approved by the DPC.

Such a process allows for alternative solutions that can lower costs over its life-cycle, said Ms Indranee.

She cited how the Maritime and Port Authority of Singapore devised a method of reusing excavated and dredged materials from other sites for its land reclamation when constructing phase one of the Tuas mega port.

"This saved a few hundred million dollars by reducing the amount of sand needed," she said.

Ms Indranee also noted that a project must be re-approved if there are material changes to its scope at any stage, or if the project cost increases by more than 10 per cent or $100 million.

The agency involved has to provide justifications for the changes, which are scrutinised again by MOF, before seeking re-approval from DPC.