Qantas chief executive Alan Joyce says he supports the Federal Government's carbon tax in principle, but says the company needs to see more details.

Prime Minister Julia Gillard wants to introduce a fixed price on carbon in July 2012, but the Federal Government has not yet determined the tax level.

Mr Joyce is a member of the Government's business roundtable on climate change.

He says if the carbon price is between $20 and $30 a ton it could take $100 million off the airline's annual profit.

He says the cost would be passed on to customers and estimates it would be around $6 extra per domestic flight.

"Apparently what we're looking at is that we can't digest the full cost of the carbon costs. We believe that it will need to be passed on to passengers," he told ABC's 7.30.

"But in the terms of the scope of the airfares, we carry a lot of people domestically and we're talking about something in the region of maybe around $6 a passenger in the domestic market.

"The ability for us to pass on will obviously at the time depend on how robust the market is, how robust demand is, but it would be our intention that it would have to be passed on to the passengers, because the margins that we make in this business isn't sufficient enough for us to digest this charge."

Mr Joyce says he understands why the Government wants to price carbon, and says the consultation process has been good.

But he says he needs more detail on the plan before he supports it.

"The devil is in the detail on this - and of course we have a lot of work that needs to be done with the roundtable and the working groups around the roundtable and the detail of how this will apply and what the mechanisms will be and whether those principles are abided by will be key to this," he said.

"We believe that certainly should be a given to the industry.

"We're buying aircraft that are going to be operating for the next 20 years, so very important for us to have certainty about what the carbon price is going to be."

Mr Joyce says the revenue raised from the tax should be directed towards technology to reduce emissions.