New Zealand's national airline says it is trialling edible coffee cups in a bid to reduce the amount of waste on board its planes.
The cups, by local company Twiice, are made from vanilla-flavoured biscotti - and are apparently "leak-proof".
Air New Zealand, which serves more than eight million cups of coffee a year, said it wanted to reduce the amount of waste sent to landfills.
But some said a change in cups was not a big enough environmental commitment.
In a statement, Air New Zealand said the coffee cups were being tested "in the air and on the ground" as part of its efforts to find "innovative ways to meet sustainability challenges".
"The cups have been a big hit with the customers who have used these, and we've also been using the cups as dessert bowls," Air New Zealand's Niki Chave said.
Jamie Cashmore, the co-founder of Twiice, said the cups "could have a really positive impact on the environment".
In the UK, some 2.5 billion coffee cups are estimated to be thrown away each year and only 0.25% of them are recycled.
Air New Zealand said the trial of edible cups followed a recent switch to compostable cups made of paper and corn, used in all of its aircraft and lounges.
But some social media users said the airline needed to change more than coffee cups if it wanted to help the environment.
Flights produce greenhouse gases from burning fuel, which contribute to global warming when released into the atmosphere.
"So good to see an airline minimising its environmental impacts. Oh, hang on a minute...", environmental journalist George Monbiot wrote sarcastically on Twitter.
"How about reducing emissions", another Twitter user wrote. "Maybe just cancel one flight a week to London instead", said another.
Air New Zealand has also been fielding concerns from customers on Twitter about dietary requirements. It told a vegan customer that the cups contained egg, while Twiice said the cups also contained gluten and might contain traces of nut and dairy.
The airline has stressed that its plant-based cups will continue to be available on all flights during the trial.