When global climate change activist and Time Magazine Person of the Year, Greta Thunberg, coined the term "flight shaming", the ripple effect was felt as far away as Canada.
From its headquarters in Quebec, the International Air Transport Association (IATA) is busy mounting a defence.
Director-general and CEO of IATA, Alexandre de Juniac, said that while he acknowledged the growing movement, which is gaining traction by the day due to the amount of publicity it receives, it comes at the expense of commercial aviation.
However, he said, many people are unaware that environmental sustainability has always ranked high on the aviation industry's agenda.
Setting the record straight
The IATA CEO said today's aircraft emit about 50% less carbon monoxide and 90% less smoke and unburned hydrocarbons compared to jets made 50 years ago.
In fact, he said, carbon emissions from the average trip are half of what they were 30 years ago.
Since 2008, airlines, airports, equipment manufacturers and air navigation service providers have agreed to reduce carbon dioxide (CO²) emissions -- which accounts for 2% of all human-generated CO² (see graphic). This is achievable by means of capping net emissions from 2020, before cutting them in half by 2050, compared to 2005 levels.
In 2016, members of the International Civil Aviation Organisation (ICAO), a specialised body of the United Nations devoted to civil aviation, agreed to the vision of carbon-neutral growth from 2020. The mechanism to make it happen is the Carbon Offset and Reduction Scheme for International Aviation (Corsia).
"The industry has also taken the lead in identifying, testing and certifying sustainable alternative fuels, which we believe can reduce our carbon footprint by 80%," according to Mr de Juniac.
His often-emphasised message is clear -- flying isn't the culprit, carbon is.
Getting its act together
Commercial flying accounts for about 2% of global carbon emissions and about 12% of transport emissions, according to the Air Transport Action Group.
The survey found that the percentage of people thinking of reducing their flying had climbed to 27%, up from 20% in a previous survey in May this year.
This is also reflected in IATA's own survey, which shows that air travel frequency is plateauing in developed markets but is rising in emerging markets (see graphic).
The airline industry has taken stock of the trend, although experts agree "flight shaming" probably has little to do with it. However, the industry feels the compelling need to get its environmental act in order, as cleaner skies also bode well for the airlines' balance sheets.
Practical approaches are being explored so as not to keep aircraft in the air longer than necessary. These include promoting direct routes and taking measures to prevent aircraft being ordered into a holding pattern before landing.
The amount of waste generated by inflight catering shows how flying can be unkind to the environment, he said.
The average passenger generates 1.43kg of water per flight -- and the amount is expected to double in the next 10 years. Over 20% of the waste is untouched food and beverages -- equivalent to about US$4.5 billion (135.9 billion baht) per year.
This prompted a response from IATA, which then issued cabin waste recycling guidelines.
In May, 150 industry stakeholders met at the Sustainable Cabin Forum to discuss technical solutions which support the circular economy and reduce industry costs. The result was the publication of a handbook to provide best practice on cabin waste management, according to Jon Godson, IATA's executive for Environment Best Practices.
A boon or bane?
At the same time, efforts to deliberately suppress air travel through punitive passenger taxes are inefficient and largely ineffective at curbing carbon, said Mr de Juniac, citing a series of decisions made in recent months to levy air passenger taxes, including in France, Germany, the Netherlands and Switzerland.
Corsia's effectiveness lies in its global scope. The scheme, he said, is estimated to reduce emissions by around 2.5 billion tonnes over the scheme's lifetime.
However, he said, the global goodwill towards implementing Corsia is compromised by governments issuing a patchwork of carbon taxes.
"Taxation aimed at stopping people from exercising their freedom to fly will make travel more expensive but do very little to reduce emissions," said Mr de Juniac.
"It is a politician's feel-good solution, without taking responsibility for the negative impact it has on the economy or the mobility restrictions it imposes on people with lower incomes."
In the long-run, the industry aims to bring emissions down by using cleaner technology. According to Mr de Juniac, this will require a financially sound sector, capable of funding the significant investments which will be needed to make flying sustainable.
"Government leadership is needed to incentivise the commercialisation of sustainable aviation fuels, improve efficiency in air traffic management and support research into next-generation low-carbon energy sources," he said.
According to IATA, carbon offsetting through Corsia is not intended to replace these efforts, nor would it make fuel efficiency any less of a priority. Rather, it said, Corsia can help the sector achieve its climate targets in the short and medium term by complementing emissions reduction initiatives within the sector.
Carrie Harris, Group Sustainability Manager of the International Airlines Group (IAG), agreed the industry needs a lot of support to help reduce its emission levels -- especially for the scale-up of the use of sustainable aviation fuels.
"Governments should create policies which favour sustainable aviation fuels, de-risk new technology investments and support fuel testing research and development to increase supply," she said.
Making adjustments
For Swiss International Airlines (SWISS), the most effective way to reduce flight emissions is to use advanced, more efficient aircraft. The airline is investing over eight billion francs (245.7 billion baht) over a 10-year period to modernise its fleet.
Its new Airbus A220s consume some 25% less fuel than the aircraft the model replaces. And the Airbus A320neo -- which SWISS plans to deploy on its short- and medium-haul routes from 2020 onwards -- will contribute to reducing carbon dioxide emissions, the airline said.
Thai AirAsia, meanwhile, also stressed it had already implemented measures to reduce its CO² emissions and voiced its support of Corsia, which it believes will help support airlines to fund projects to offset their carbon footprints and keep emissions in check.
"We are working with the Civil Aviation Authority of Thailand to further promoted Corsia, and we are adopting sustainability as an internal strategy, by adopting advanced technologies, improving operations, switching to alternative energy sources and other market-specific measures," said Thai AirAsia's CEO, Santisuk Klongchaiya.
The region's leading low-cost carrier said the effective use of the right fuel to power aircraft and run the industry, and even the economy, is crucial to sustainability.
"We believe that in the future, technology will come up with a clean and appropriate method to truly reduce carbon emissions," he said.
In the meantime, aircraft manufacturing giants Airbus and Boeing, are rolling out technologically-advanced aircraft which are more fuel-efficient, able to fly further and accommodate more passengers than previous models while reducing costs and stretching profits.
"Thai AirAsia acknowledges the environmental concerns and issues that have been raised," Mr Santisuk said, adding emissions are likely to shrink in the years ahead thanks in part to effective air travel management and innovations in biofuel, which is being seriously explored.
According to IAG, 80% of flights connect city pairs which are at least 1500km apart, where no realistic alternative to flying exist.