Air New Zealand's voluntary programme of selling carbon credits to travellers is failing to take off.

The airline launched the programme in March, allowing customers to buy carbon credits to offset the environmental impact of flights within New Zealand.

Air New Zealand says so far, only 1% of customers have bought credits. A return flight for one traveller between Auckland and Wellington costs $4.50 to offset.

Air New Zealand's chief executive Rob Fyfe says the airline is to start marketing its carbon offset scheme. He says the airline has bought hundreds of thousands of carbon credits in the expectation it can on-sell them to customers.

The New Zealand Exchange's carbon trading platform, TZ1, is educating companies about the emerging market.

Chief executive Mark Franklin says a 1% up-take in a voluntary carbon offset scheme is in line with overseas trends.

Mr Franklin says because carbon trading is an emerging market and many companies and individuals do not have a basic understanding of it, uptake is likely to be slow.