The latest big number on the impact of ''flygskam'' - or flight shaming - should have the aviation industry's attention.
It doesn't come from an environmental group's social media campaign, or a pronouncement from teen activist Greta Thunberg.
This is hard-nosed research by an investment bank which makes clear that the future of flying and the enormous industry surrounding it is uncertain because of concerns about the climate.
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That's worrying for airlines and tourism industries such as New Zealand's, which vies with dairy as our biggest foreign exchange earner, but it's also a reminder of the opportunity that aviation and the energy sector must now seize.
The UBS research has revealed that travellers are already choosing not to fly, with 21 per cent of the 6000 people polled in the United States, Germany, France and Britain saying they had reduced the number of flights they had taken during the past year, because of the environmental impact.
If current trends continue, this could halve the growth rate in passenger numbers.
Of those surveyed, 16 per cent of British respondents said they were cutting back on the number of flights while 24 per cent of those in the US said they were flying less. Both are key tourism markets for New Zealand.
And according to the BBC's take on the UBS report, the number of flights in the European Union will increase by 1.5 per cent a year, half the rate expected by planemaker Airbus.
The bank forecast that growth in US flights would fall from 2.1 per cent to just 1.3 per cent.
While it doesn't specify the impact on airlines, it says the planemakers will be hit.
The number of smaller planes ordered from Airbus and rival Boeing would fall by 110 each year.
This would reduce revenue at Airbus alone by about $5 billion a year.
Already, Scandinavian airline SAS has experienced a 2 per cent cut in traffic this year and Swedish airports say domestic traffic is down by 8-10 per cent this year.
For New Zealand it's hard to pinpoint the impact of this growing flygskam movement, one of whose early symbols was Thunberg's mother Malena Ernman.
The overall rate of growth in visitors to New Zealand is well off its nearly double-digit peak of a few years ago. Growth of the British market has softened in the past year, which has been attributed to Brexit uncertainty and the weaker pound, but the German market has also weakened.
Arrivals from the US are surging, though.
Around the world, 4 billion passengers travel every year and this is expected to nearly double by 2036.
Within that time one report says the aviation sector alone could emit a quarter of the world's remaining carbon budget – the amount of carbon dioxide emissions allowed if global temperature rise is to stay below 1.5C.
New aircraft and engine technology have helped over the past 30 years but the rate of fuel efficiency gains is slowing.
Every flight taken by a passenger today will produce half the CO2 that the same flight would have emitted in 1990, and while the industry's long-term goal to halve net total CO2 emissions by 2050, that's aspirational. Without a massive shift away from today's fuel for planes - dirty kerosene - that goal is likely to remain on the wish list.
Contrails from aircraft exhausts could have an even greater impact on global warming than carbon emissions, so aviation will remain a big target for environmental crusaders and environmentally conscious passengers who have alternatives to flying.
And that's a big problem for New Zealand. Nearly all our visitors have to fly here and once they are in this country our rudimentary long distance rail and bus network doesn't provide a viable alternative for them - or locals - who want to travel long distance in a hurry.
Twelve hours on a train between Auckland and Wellington - compared to a one-hour flight - doesn't add up for anyone on a tight timetable.
This week's UBS report has some stark, scary numbers but it won't come as a surprise to airlines and the tourism industry in this part of the world.
But there's a renewed focus on the issue, and during a Tourism Industry Aotearoa roadshow this year it was the most consistently voiced concern of all operators.
A Ministry of Business, Innovation and Employment report this month said growing global concerns about climate change, environmental degradation and wider sustainability practices represent a threat to international travel to New Zealand in particular.
''Growing awareness and concern about carbon emissions are predicted to have a significant effect on travel choices globally over coming years. Given New Zealand's distance from most source markets, the potential implications for our international tourism industry of travellers' carbon emission concerns is not to be ignored; careful reflection by our tourism industry is required.''
Air New Zealand has identified the response to the climate ''crisis'' as pivotal and a member of the airline's sustainability advisory panel, Tim Jackson, has spelt out the uncomfortable place where the company, and this country, finds itself.
'When you're living in the middle of a vast ocean 2000km from the nearest country, the last thing you want to hear about is flygskam,'' says the professor of sustainable development at the University of Surrey.
He says a return flight from Auckland to London accounts for about four tonnes of carbon dioxide, 10 times the annual carbon footprint of an average Bangladeshi.
''Flying must either find a way to go fossil-free or else there must be fewer air miles factored in to a business plan rather than more and more each year. Waiting for it to blow over is not really an option.''
The airline's sustainability report also delivered the unwelcome news that emissions in the past year had grown 5 per cent because of network growth and being forced to use older aircraft to substitute for grounded new-generation Dreamliners.
What's the answer?
Offsetting is one way of paying more to fly in order to support carbon reduction projects - such as forests - that generate carbon credits.
On Air New Zealand it will cost you $2.76 to offset a return flight between Auckland and Wellington, $7.58 between Auckland and Sydney and $32.74 between Auckland and Los Angeles.
The problem for the airline — and the planet — is that not many passengers do it, with Kiwis just ahead of Aussies near the bottom of the pack.
Former Air NZ chief executive Christopher Luxon said while up to 20 per cent of travellers claim they did, just 4.6 per cent of New Zealanders offset their flights. This compares with 7.3 per cent of North American passengers and nearly 10 per cent of those from Britain.
During the past year 184,000 journeys were offset, up from 130,000 the previous year, although this is a tiny fraction of the 17 million passengers carried.
The only real solution is biofuel, sustainably produced and suitable to drop into aircraft tanks and the on-ground infrastructure. In this area, progress has been glacial compared to the rate at which glaciers are melting.
Since 2011 there have been 200,000 biofuel blend flights - around the same number of flights in just one day in the peak of the northern summer last year.
There hasn't been the financial imperative, the will or the government support to replace more of the estimated 367 billion litres used every year by the airline industry.
When oil spiked to more than $US100 a barrel in 2008, there was a surge of enthusiasm, and Air NZ and other airlines ran short lived trials. But it's been slow going since then.
Air New Zealand says it has joined with Z Energy, Refining NZ, Scion and Auckland International Airport to investigate setting up an aviation biofuel plant.
Z has struggled for nearly three years to get its Wiri plant producing biodiesel for trucks running on a commercial scale.
The complexity of building the plant from scratch rather than off the shelf meant it was late last year before it began supplying Fonterra with small quantities of tallow-derived fuel. Getting the fuel specifications right for planes will be far more exacting; at 35,000 feet there is no margin for error.
Sheena Thomas, Z Energy's fuel strategy manager, says aviation biofuel would probably come from woody waste - initially the byproduct of forestry processing and, if adopted on a wide scale, from specially grown forests on marginal land. This would provide opportunities for growth in the regions.
She says there is need for a ''national conversation'' - in other words, government support - to get this off the ground.
In its sustainability report, Air NZ says there is a lack of clear policy incentives to take the plunge into full scale jet biofuel.
''The capital investment would be significant and it has not been achieved anywhere in the world without substantial government support to establish production and thereafter ensure fuel pricing remains viable.''
What's the Government doing?
Nothing specifically for the aviation sector at the moment.
A spokesman for Energy Minister Megan Woods said: ''The Government does not have any new policy proposals specific to aviation biofuel but it is an area we are interested in.''
Government agencies were looking into opportunities for the use of biofuels in the transport sector, and more broadly the use of bioenergy across the economy.
The Government's overall strategic direction is to encourage a shift towards renewable energy so that we can successfully transition to a low-carbon future.
Biofuels could potentially contribute to this transition, depending on whether biofuels could become economically feasible and more competitive relative to other renewable energy sources in the long term, the spokesman said.
Asked whether there were any incentives for biofuel development, he said the Government focussed primarily on research and development (R&D) investments.
The Strategic Science Investment Fund (SSIF) supports longer term programmes of mission-led science and scienceinfrastructure of enduring importance to the future of New Zealand's economy, environment and wellbeing.
Crown Research Institute Scion receives $17.4 million a year of Strategic Science Investment Fund money of which $7.4 million goes in to the development of bio-based manufacturing and products fromwood fibre, waste and other biomaterials.
The Government also provides funding to research institutes' biofuels-related projects through the Endeavour Fund Smart Ideas investment mechanism.
Biofuels project developers can also explore co-investment opportunities with New Zealand Green Investment Finance, a green investment bank established by the Government. Its purpose is to accelerate investment to lower greenhouse gas emissions activities in New Zealand.
The Provincial Growth Fund is another option that biofuels project developers can explore, the spokesman said.
''More broadly, the Government is focusing on getting the regulatory settings right to promote innovation, accelerate the uptake of technology and shift towards a more productive and high-tech economy.''
Part of this was the restoration of R&D tax credits announced last week as part of the Government's aim to increase spending on R&D to 2 per cent of GDP.
What airlines in this region are doing
Across the Tasman, Virgin Australia and Qanas are also pushing for government support.
Virgin has done some research with Air New Zealand, but as that alliance ended, so has that work.
Since that announcement the Australian airline has been operating biofuel flights in partnership with US-based biofuel producer Gevo and supply chain partners Caltex and DB Schenker for a year, with the Queensland Government and Brisbane Airport.
The bio fuel comes from carbohydrate sources (such as non-food corn starch) converted into isobutanol (alcohol) and further processed into sustainable jet fuel, which is blended with traditional jet fuel.
By the end of the trial, more than 700 flights had flown more than 1 million kilometres using the sustainable aviation fuel mix.
This project has been an important step in ensuring Australian airports and the fuel supply chain will be ready for the regular supply of sustainable fuels in Australia.
''However, in order to enable low carbon sustainable aviation fuels to succeed, they must be able to compete on price. Government support will be needed to develop a thriving, local industry,'' the airline says.
Qantas and Air New Zealand, now friends, have raised the possibility of collaborating on biofuel projects.
It operated the first biofuel flight across the Pacific last year using industrial mustard seeds.
It has entered into an offtake agreement for renewable jet fuel from SG Preston in the United States, which is 50 per cent produced from non-food plant oils. This fuel will emit half the amount of carbon emissions over its life cycle compared to conventional jet fuel.
''When this fuel is produced, we will be taking 111 million litres a year out of Los Angeles when up and running,'' a Qantas spokesman said.
The airline was also working closely with other airlines and fuel producers to accelerate the development of a market for sustainable aviation fuels in Australia.
''But, as Air NZ and Virgin have raised, the policy settings by governments in this part of the world have to be right for bio-fuel projects to stack up.''
Greenpeace in New Zealand agrees the Government should be investing ''heavily'' to clean up the energy system and provide support for truly sustainable aviation fuels.
But airlines should pay their way.
"Air New Zealand is a very profitable business that has made a lot of money off of burning dirty fuels. To date, they haven't had to pay for their industry's sizeable impact on the climate,'' says Amanda Larsson, Greenpeace New Zealand climate and energy campaigner.
She goes further, pushing back at flying.
"Biofuels are far from the whole story. Aviation needs to stop expanding and instead be significantly scaled back. We also need to see investment in alternatives to flying.''
There was potential in New Zealand for fast passenger rail services so that there are alternatives.
Larsson says oil companies such Austrian OMV should divert the hundreds of millions of dollars invested in searching for new oil and gas off the coast of Taranaki and Otago to spending on developing alternatives.
''Aviation would be in a different place if the oil and gas industry instead spent money like this on developing sustainable fuels."
Alarm about ''food miles'' was the big scare for our primary exporters a decade ago.
There was a push by environmentalists (and European farmers) to shun products shipped half way around the world and to buy local instead. In a pre-social media world this had a negligible impact on exporters but the current concern about pollution from air travel has the potential to develop into something much more significant for this country.
