Air New Zealand says the number of people opting in to its FlyNeutral programme has risen this year - but not by as much as they said in February.
The FlyNeutral programme allows air travellers to pay an optional extra fee when buying a ticket to offset the carbon produced by their travel.
The fee essentially goes towards paying for a part of a native forest to be grown, which absorbs carbon from the atmosphere.
Air New Zealand has not incorporated the fee into its fare structure, nor opted to pay the fee itself, saying it would rather "give customers the option".
In February this year, Air New Zealand head of sustainability Lisa Daniell told Breakfast the FlyNeutral uptake rate was 11.4 per cent.
However, that figure is at odds with Air New Zealand's latest sustainability report, released today, which reports an uptake rate of 7.1 per cent.
A spokesperson for Air New Zealand said "some of our international storefronts have consistently had uptake rates over 10 per cent during the year, but the 7.1 per cent figure represents the average uptake across all storefronts for the full year.
"For example, at one stage pre-Covid our UK storefront recorded uptake of over 16 per cent.
"The percentage uptakes have fallen slightly due to the impact of Covid-19, but the fact customer uptake rates have remained reasonably stable throughout the pandemic is really positive and shows people are still thinking about the impact of flying."
CEO Greg Foran said it had been a "challenging" year for the aviation sector, and that "we have worked hard to ensure the actions we have taken over past months will enable the airline to emerge competitively and sustainably from the Covid-19 crisis.
"It has been particularly pleasing to see voluntary offsetting rates increase in the past year – through our voluntary carbon offsetting function FlyNeutral, together with our customers we have contributed close to $1.5 million towards permanent native forestry projects across New Zealand and achieved an average uptake rate across all retail storefronts of 7.1 per cent, which is fantastic when you take into account the drop off in passenger numbers this year.
"Thank you to all our customers who continue to choose to offset their emissions."