The proposed flight path for the airport's 24-hour facility was announced on Tuesday, with residents in the suburbs of Mount Druitt, Penrith, Prospect, Orchard Hills, Bankstown, Windsor and Richmond likely to be the most affected.

People living in the Blue Mountains will also be affected, but to a lesser extent.

Experts are divided on the impact on property values.

Sam Powell, a real estate investment consultant and head of analysis at Hello Haus, said it would be a "fair assumption" to say that property values would be affected in the suburbs under the flight path.

"Historically, they have not performed as well as the surrounding areas for obvious reasons, and noise is a huge issue," he said.

"The methodology I use is to look at the sales prices of similar properties with similar acreage and improvements under the flight path and without the flight path.

"There is a clear indication that they are selling at a discount due to the impact and lower level of desirability/attractiveness to owners."

Mr. Powell said that building new homes with provisions around flight paths will also be a consideration for buyers.

"It could lead to more expensive building materials, which is also undesirable," he said.

The initial impact of flight paths will come down to the "human psychology" of buyers, he said.

"They will no longer be keen to look for homes in the area," he said.

"It will be a secondary or even a third location for them."

Mr Powell said if Sydney saw a decline or a neutral market, it could classify areas such as Druitt Hill as "undesirable" and cause prices to fall.

"Overall, the value of the area will increase along with the surrounding suburbs due to (current) supply and demand, however, they will always be seen as less popular and prices will reflect that," he said.

He noted that a study by the University of Sydney found that properties under flight paths were worth three to five percentage points less than other properties.

"In the long run it will become a new norm and people will expect a little discount, but that won't stop people buying there if it suits their ability," he said.

Mr. Powell said that while proximity to the airport is desirable for travel, people should consider their "opportunity cost."

"If you had a million dollars to spend, where would you spend it? My view is to try not to spend it under the flight path," he said.

"You might not get the completely separate house you want, but you might get a nice big semi that's not under the flight path. You'll get better capital growth out of it because it doesn't have those negatives."

Vanessa Rader, director of business research at Ray White, said that while there will be noise impacts, the government is doing a good job of limiting the impact, with more heavy aircraft movement in the Southeast, where population densities are lower and there is more employment-related land.

"In terms of value, the results have been mixed, and this region has gone through an outstanding period of growth in housing values," she said.

That growth, she said, has been spurred by investments in infrastructure.

"Historically, land value appreciation in the area around Aerotropolis has been sound, and given the current mismatch between supply and demand across Sydney, price growth will continue in the future," she said.

"Buyers may take flight paths into account when buying, but location advantages, transport, schools and employment opportunities are all considerations, and some may argue that these have improved with the development of the airport.

"As for commercial investment, over the last few years we have seen a huge attraction in the area. Western Sydney is expected to be the recipient of most of Sydney's growth population, so it makes sense for all types of investment to be focused on that area."

Ms Rader said buyers in Sydney's inner west were initially reluctant when the third runway at Sydney Airport opened in the mid-1990s.

"Since then, we have seen these markets enjoy strong levels of capital value growth at a similar rate to the market across Sydney," she said.

"These suburbs provide excellent access to the CBD and were once quite affordable, but are now growing along with the rest of Sydney.

She said the "proposed route" for Western Sydney Airport was still under negotiation.

"The advantages of being close to Sydney's largest infrastructure project, with improved access, transport and employment opportunities, may offset some of these impacts," she said,

Over time, we have seen the impacts diminish, as in the case of the Inner West, but given Sydney's current housing supply, this will also ease the uncertainty of value for many homeowners," she said."

Peter Diamantidis, principal of the Ray White Diamantidis Group, said his phone calls have been hot since the flight path was announced.

"My message has been 'it's not going to affect us,'" he said.

"If anything, I think home values will go up. People will be close to a national airport that runs 24 hours a day. Why would it go down?"

He said the market in Western Sydney has been booming since news of the Western Sydney Metro and Western Sydney Airport broke.

"There's been a massive increase in investors and first-time buyers," he said.

"People aren't suddenly leaving because of the construction of the airport.

"What's the difference between living near a train line or near a freeway? I think it's going to be a positive for the area."