Faced with the climate crisis, the debate over whether Government ministers should fly business or economy class sounds like moving the seats around on Air Titanic.
There is, after all, no such thing as low-carbon flying – no matter what level of comfort or confinement your seat offers.
But turning left or right when boarding the plane can influence how high your personal emissions ascend.
So the admission by two Green Party ministers that they have stepped left into business class on work trips warrants scrutiny.
According to the International Council on Clean Transportation (ICCT), a passenger travelling business class or first class emits up to four times more carbon per air mile than a fellow traveller in the cheap seats.
At first glance, that doesn’t seem to make much sense as the plane is flying, using fuel and spewing out carbon regardless of how many passengers are on board and where they are seated.
The logic is that the more passengers can be crammed into economy, the more efficient the use of fuel is and the greater number of heads there are to divide the emissions between them to give a lower ‘per passenger’ carbon footprint.
On the other hand, the premium section of the aircraft will have fewer people and carry marginally less weight than the crammed economy section and with weight being the main determinant of fuel use, the flight will save a little on fuel and emissions.
But for every budget passenger who can’t be accommodated on a plane because space is taken up with roomy business-class accommodation and cavernous first-class quarters, another seat is needed on another flight.
All those squeezed-out, cheap-seat passengers will eventually make up another full plane-load so there are more aircraft flying and therefore more industry emissions overall.
Business-class travel has another, less obvious, emissions-growing effect, in that its high-price tickets effectively subsidise economy class, keeping seat prices low and passenger numbers, flight counts and emissions high.
Brussels-based campaign group, Transport and Environment (T&E) referred to this tangled relationship between budget and business seats in an aviation decarbonisation road-map report last March.
“Even though business travellers make up a small share (about 20pc) of total passengers, they generate a substantial part of airlines’ revenues, up to 75pc according to some sources,” it said.
Any loss of that income would have to be made up by raising the price of budget seats which would dampen demand.
T&E calculated that a 50pc reduction in business passengers could result in at least a 4pc drop in economy passengers “even if aircraft configurations are adapted to reduce premium seats in favour of economy seats”.
That 4pc drop would be significant as it would come off a much higher number than the business passenger base.
A reduction in business-class passengers could be achieved in a number of ways. Companies, the biggest customer for premium seats, may take the initiative themselves.
They are under pressure to deliver corporate carbon-cutting measures so restricting flying time or switching to economy is a relatively easy target.
Matteo Mirolo, aviation policy officer with T&E, said passengers may need a stronger nudge and that business-class seats, expensive as they are, need to be even more so as there comes a point when accountants in even the biggest companies start questioning expenses.
“Flying business class is four times worse for the climate than economy,” Mr Mirolo said.
“There are two solutions – stop flying business class and ideally replace your flight by low-carbon alternatives where possible.
“And for those who do fly business (class), we need to apply higher taxes on business class to reflect the disproportionate climate impact of those seats.”
Mr Mirolo had little sympathy with the argument that government ministers such as Eamon Ryan and Catherine Martin need space and privacy on flights to work and to arrive fresh for whatever negotiations their flight is taking them to.
“When faced with such a climate emergency, ministers should have better things in mind than flying in luxury,” he said.
The airline industry has pledged to be carbon-neutral by 2050 and whatever about the credibility of that stated ambition, the EU is developing an initiative, called ReFuelEU, to boost the supply of sustainable aviation fuel (SAF).
Last week, the European Parliament banned palm oil and other biofuels that come from environmentally destructive monoculture from being used in SAF.
The emphasis is being placed instead on e-kerosene, a synthetic fuel made from green hydrogen and carbon dioxide.
Technically, these synthetic fuels have been proven to work, and some airlines are already mixing a small percentage with their regular fuels to begin the transition.
They are costly, however, and will continue to be until the technology is widely replicated and economies of scale chip away at price.
Carbon-neutral may be the future destination but in the meantime, airlines will be quietly hopeful that discerning – in other words, wealthy – passengers will continue to know their left from their right.