The flight path for the Badgerys Creek. But the Environment Department ruled on December 23 that World Heritage impacts must be examined, after protest submissions by environment groups and the former Howard government minister Jackie Kelly. The Blue Mountains was finally accepted on the World Heritage list in December 2000, within a fortnight of the Howard government publicly announcing that plans for Badgerys Creek had been shelved. Correspondence between UNESCO and the Australian government earlier in 2000 had shown the government backing away from a second airport. UNESCO advisers had earlier cited the risk of airborne fuel emissions, visual intrusion, and predicted aircraft noise of 70 to 80 decibels as "adversely affecting the natural quiet" of the Blue Mountains area. The World Heritage listing states "proposals for a second Sydney airport at Badgerys Creek ... have been abandoned".

A UNESCO spokeswoman in Paris told The Sun-Herald the World Heritage Committee hadn't been informed the Abbott government had revived the airport project, which is eight kilometres from the World Heritage area. This is despite the convention requiring governments to notify any intention of new construction – before basic documents are drafted or decisions made. "UNESCO will surely follow up with the Australian authorities," she said. The International Union for the Conservation of Nature, the committee's advisory body, would require "detailed information for review". A spokesman for Infrastructure Minister Warren Truss said "improvements in aircraft technology and regulatory standards" meant the noise and air pollution risk was lower than previously assessed in 1999. But Mrs Kelly, a former RAAF officer, rejected this claim, arguing the threat to the Blue Mountains of takeoffs and landings is significant.

Colong Foundation For Wilderness director Keith Muir accused the department of being "sneaky". "They were trying to dodge a bullet, and have an environmental assessment that would not have to look at World Heritage," he said. Mrs Kelly, who is an independent candidate for the seat of Penrith at the NSW election, said there was "no doubt" flights will be routed over the Blue Mountains because of the political need to minimise noise in marginal Liberal western suburbs seats . "At Mascot, 55 per cent of flights are over the ocean. Fifty five per cent of flights will be over the Blue Mountains. All of that aviation gas pollution and noise pollution over World Heritage areas," she said. Mrs Kelly said she was campaigning against the airport in the Liberal-held seat of Penrith because she didn't see why the promised infrastructure funding package for Western Sydney had to be tied to an airport. "I think at the moment if you say 'jobs', people will put up with anything. But when people realise how many jobs, what kind of jobs, and the trade-off in enjoyment, property values and traffic congestion, it will be one big sticky do." Mr Muir said the Infrastructure Department had claimed in the document that noise wouldn't be a significant impact for the Blue Mountains because there were already aircraft flying over at higher altitudes.

"That's like saying if there is one freeway in metropolitan Sydney, a second freeway would have no impact. That is factually incorrect." Mr Truss' spokesman said the airport proposal would see air traffic approach and depart over the Blue Mountains, which "may generate some indirect noise and pollution impacts on some areas of the Greater Blue Mountains". "Aircraft at a Western Sydney airport are not expected to represent a new source of impact on the aesthetic and wilderness values of the Greater Blue Mountains," the spokesman said. A spokesman for Environment Minister Greg Hunt said rather than pre-empt the findings, the government will await the completion of the environment assessment that is being undertaken. He said the approval process will take into account scientific evidence and public comments. Mr Hunt's spokesman said the proposed airport is outside the Blue Mountains World Heritage Area, but as a "matter of good faith" UNESCO would be advised in the regular quarterly update. He said there had been no suggestion of losing World Heritage status in discussions with UNESCO over contentious plans to expand a port in another World Heritage property, the Great Barrier Reef. However the World Heritage Committee will consider placing the Great Barrier Reef on the "in danger" list next year, a step towards delisting.

Blue Mountains World Heritage Institute executive director Rosalie Chapple said conservationists need to start planning for the impact of increased tourists in the Blue Mountains. "The airport will increase visitations and people living up here. There will be knock-on effects," she said. "People take it for granted that the Blue Mountains is World Heritage listed, but it has not brought any more money into the management of the property."