Every advert that quietly slips in "carbon neutral flight" is asking the reader to trust something they cannot see. Most of us do trust it, briefly, when we tick the little green box at the end of a booking. The flight leaves. The email arrives. Life carries on.
It is worth pausing on what actually happened in that moment. A small payment moved. A credit was retired somewhere. And a carbon question, which is genuinely complex, was quietly closed off with the words "carbon neutral" on a receipt.
This article is not a case against offsetting a flight. It is a case for doing it honestly, if you are going to do it at all. What follows is what your money actually pays for, what it cannot legitimately claim, and how to tell a scheme worth trusting from one that is doing you a quiet disservice.
Table of contents
What offsetting a flight actually is
Offsetting a flight means paying for a project that reduces or removes greenhouse gas emissions elsewhere, in an amount equivalent to what your flight emits. It does not remove the emissions from your flight. The plane still burns fuel. The CO2 still enters the atmosphere. What changes is that a separate, verified activity has taken place somewhere else in the world, and its emissions credit has been retired in your name. This is a genuine action. It is also a limited one. Understanding both parts is the difference between offsetting well and offsetting as reassurance
How flight emissions are calculated
For any offsetting number to mean anything, the flight emissions figure it is based on has to be honest. That is trickier than it sounds. The UK's standard approach comes from the Department for Energy Security and Net Zero's greenhouse gas conversion factors, published each year. The method takes the distance of the flight, applies a per-passenger-kilometre emissions factor for the aircraft class (short-haul, long-haul, economy, business), and returns a figure in kilograms of CO2 equivalent. Government departments and most reputable calculators use this approach (DfT journey emissions methodology). The DESNZ factors themselves also add an 8% uplift to account for indirect flight paths and delays, because planes rarely fly the shortest possible route.
Here is what many booking-page calculators leave out. Aircraft do not only emit CO2. At altitude, they also produce nitrogen oxides, water vapour, sulphates and particulates, and they create contrails. These non-CO2 effects add to the warming impact of a flight in ways that CO2 alone does not capture.
The DESNZ conversion factors note that users may need to apply a 1.7 multiplier to the CO2 figure to account for these radiative forcing effects (DESNZ 2025 GHG conversion factors, aviation notes). That is a significant uplift. A long-haul flight quoted at 1.5 tonnes of CO2 might have a warming impact closer to 2.5 tonnes once altitude effects are counted. Most airline "carbon offset" checkout boxes do not apply this multiplier. Which means the amount you are being asked to offset is often the tidy CO2 number, not the full climate impact. Worth knowing.
What your offset actually pays for
Not all carbon credits do the same thing. This distinction matters more than the price.
Avoidance and reduction credits
These are credits generated by activities that prevent or reduce emissions relative to a defined baseline. Common examples include renewable energy projects that displace fossil fuel generation, or improved cookstove programmes that reduce fuel use in households. If the project genuinely does what it claims, and if the baseline is sound, these credits represent emissions that did not happen.
They do not, however, remove any carbon already in the atmosphere.
Removal credits
These credits are generated by activities that draw CO2 out of the atmosphere and store it. Reforestation and afforestation are the most common current examples. Biochar, enhanced weathering and direct air capture with storage are smaller but growing categories. Removal credits are the ones that address atmospheric CO2 that has already accumulated. They are typically more expensive, and supply is smaller. For flights, both categories can play a role, but they are answering different questions. Avoidance credits address the question "how do we prevent future emissions in the wider economy?". Removals address the question "how do we deal with CO2 that is already there, including the CO2 your flight just added?". For a more detailed comparison of the main standards behind these categories, see how the main verified standards compare.
Why "carbon neutral flight" claims have been challenged
If you have noticed that airlines have quietly stopped using the phrase "carbon neutral" in some UK advertising, this is why. The Advertising Standards Authority's guidance is unambiguous. Marketers should avoid unqualified "carbon neutral" or "net zero" claims. Where such claims are made, they must make clear whether the claim relates to actively reducing emissions or to offsetting, and to what extent (ASA guidance on carbon offsetting and carbon neutral claims).
Several airlines have been the subject of ASA rulings on this point. Lufthansa, Etihad, Air France-KLM and, most recently in July 2026, Qatar Airways, have all had adverts either withdrawn or amended. The Qatar ruling put the issue plainly: the evidence demonstrated that an offsetting programme existed, but it did not show that the emissions from specific flights would be fully offset through that scheme, or that the environmental impact of those flights was reduced ( ASA ruling on Qatar Airways Group, July 2026). That is the crux. An offsetting programme can be real. A flight's emissions still happened. Calling the flight itself neutral collapses that distinction, and the ASA has consistently ruled that consumers are misled by it.
CNB's view: This is scrutiny working as it should. It is not a reason to abandon flight offsetting. It is a reason to demand better flight offsetting, with clearer language and more honest claims. If a scheme is confident in its evidence, it can survive being described accurately.
How to choose a flight-offset scheme that stands up
If you have decided to offset a flight, and are looking at the options, here is a short checklist. Each item is a question the scheme should be able to answer.
Is it registered on a recognised standard? Look for Verra ( verra.org), the Gold Standard ( goldstandard.org), Plan Vivo ( planvivo.org) or the Climate Action Reserve ( climateactionreserve.org).
Does it publish a project ID? You should be able to look up the specific project on the registry and see its methodology, validation and verification reports.
Is the credit retired in your name? A retirement record is what turns a credit into an actual claim. Without it, you have paid for something that could theoretically be sold again.
What kind of credit is it, avoidance or removal? Both are legitimate. But they mean different things, and a scheme should be willing to tell you which.
Does it avoid claiming your flight is now neutral? A scheme that phrases its offer honestly is a good sign about the rest of its practice.
Do the prices look plausible? For a typical UK short-haul flight, expect a few pounds for a basic scheme and more for higher-quality removals. A long-haul return might range from around £15 to £40 or more, depending on the credit type. Prices well below the low end usually reflect either a very cheap avoidance credit or a scheme absorbing costs elsewhere. Worth asking why.
For a monthly approach that covers your wider footprint rather than a single flight, our subscription option may fit better. For a specific flight, our flight offset product is one route; our Travel Unravel partnership is another.
Where offsetting sits in the bigger picture
The most useful framing we can offer is this. Reducing emissions and financing verified climate action are two different jobs, and both matter. Reducing your flying, taking the train where it works, choosing direct flights over connecting ones, all change the emissions still to come. Verified removals address CO2 already in the atmosphere. Avoidance credits fund emission reductions elsewhere in the wider economy.
None of these substitutes for the others. Offsetting a flight does not undo it. Choosing to fly less does not clear the historical accumulation. This is not either-or climate action.
CNB's view: The most credible position on flying is also the calmest one. Fly when it matters. Fly less where it does not. If you do fly, offset honestly, with clear language about what your money is doing. And accept that the flight happened, that the emissions are real, and that the offset is a separate act of climate finance, not a cancellation.
A quiet note to close
There is a version of climate writing that would end this article with a list of demands. Fly less. Offset more. Buy the right scheme. Feel bad if you cannot. We are not going to do that. Most people who read this far already care, already think about it, and already do more than the average. What is missing, in this specific category, is not effort. It is honest language and evidence you can check. If offsetting a flight is a decision you want to make, make it with your eyes open. Choose a scheme with a project ID, a retirement record, a clear category of credit, and no oversold claims. The emissions still happened. The flight still went. But the action you took was real, documented and worth doing.
That is enough.
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What does it mean to offset a flight?
It means paying for a verified project, elsewhere in the world, that either reduces future emissions or removes CO2 from the atmosphere in an amount equivalent to your flight's emissions. It does not remove the emissions from the flight itself.
How many trees does it take to offset a flight?
There is no single reliable answer, because tree species, planting location, growth rate and monitoring period all vary. A verified reforestation project accounts for these factors in its methodology, which is why registry evidence matters more than a simple tree count. If a scheme gives you a neat "X trees per flight" answer without any of that context, treat it as marketing rather than measurement.
What percentage of my flights should I offset?
If you decide to offset, the honest answer is 100% of the flights you take, at the highest quality your budget allows, alongside reducing how often you fly. Offsetting a portion, or offsetting cheaply, effectively means accepting a partial answer to a full question
How much does it cost to offset a UK flight?
A short-haul return from the UK often falls somewhere between £3 and £10 for a basic avoidance credit. A long-haul return can range from £15 to £40 or more, depending on distance, class of travel and the type of credit. Removal credits sit at the higher end. Prices that look too cheap usually are.
Is a "carbon neutral flight" a real thing?
Not in the sense the phrase implies. A flight burns fuel and emits CO2. That impact is real and cannot be reversed by paying for something else to happen. What can be true is that a verified offset has been retired against the flight's emissions. That is a meaningful action worth taking. It is just not the same as the flight being neutral, which is why UK advertising rules now require clearer language ( ASA guidance on environmental claims).
