A former Qantas chief economist says overweight passengers should be paying a surcharge to fly with Australian airlines.

Tony Webber, who spent seven years with Qantas before becoming an economic consultant, says overweight passengers should be covering extra fuel costs incurred by airlines.

"When the passengers weigh more, or where there's extra weight on the aircraft, that generates more fuel burn and higher fuel costs," he said.

"Airlines are really preoccupied at the moment with reducing their fuel costs because the price of jet fuel is so high at the moment.

"On a flight from Sydney to London-Heathrow via Singapore, you're only looking at [a surcharge of] between five and 10 bucks."

Mr Webber says skinny people should also get a discount on their ticket price, as should fat people without luggage.

"In different parts of the world, for example in Indonesia, particularly rural Indonesia, they actually weigh the baggage and the passenger at the same time," he said.

"You'd have to work out the total weight of the baggage and the person and then have a critical weight, say 90 kilos or 100 kilos, above which you'd impose a surcharge."

But he says when he was at Qantas, the airline gave almost no consideration to his proposal.

He says it would be of greater interest to smaller airlines, like Jetstar and Ryanair in Europe.

"I think the low-cost carriers would be more interested than the full service airlines," he said.

"They were all thinking about how to increase fuel efficiency, and this is just one means of trying to generate revenue because of the fact that their fuel charges might have increased."

Mr Webber admits charging overweight passengers extra could be humiliating for some.

"For some people it would be humiliating, awful, and so that clearly would have some impact on the brand of the airline," he said.