The bosses at Heathrow must have been visiting another planet last week, or else they missed the government memo about legislating for net zero emissions by 2050.

The plans unveiled today for a 50% expansion in the airport by 2050, including a third runway, all to be done in “a sustainable way”, take dissembling to new levels. Heathrow is already the largest single source of carbon emissions in the UK.

The outline plans reveal the scale of what’s proposed: building a tunnel for the M25, rerouting rivers, building enormous carparks outside the perimeter of the current airport, destroying local villages. The government itself says nearly a million households will be affected by the third runway, which will allow another 700 flights a day.

The truth is that aviation growth and our expectation of cheap flights cannot continue

Heathrow’s owners maintain that the airport’s expansion will not significantly alter the UK’s emissions, but only reach this conclusion by excluding international aviation emissions. That suggests they missed another memo, this time from the committee on climate change which has said emissions from international aviation should be formally included in the UK’s climate targets.

Carbon pollution from flying in Europe has risen 26% in the past five years – far outpacing any other transport mode. And, while the UK economy has reduced its carbon emissions by 37% since 1990, CO2 from international aviation has increased by around 130%.

The government’s own draft aviation strategy is a perfect example of its have-your-cake-and-eat-it approach. The condition attached to this strategy – “provided that growth takes place in a sustainable way, with actions to mitigate the environmental impacts” – is simply unachievable.

The IPCC has already warned us that we have only 11 years left to slash global emissions in half, if we are to achieve the Paris agreement goal of limiting global warming to 1.5C. There is no technological magic wand which is going to transform aviation’s dependence on fossil fuels in this time.

We are unlikely to see a single electric aircraft big enough to carry passengers any further than the distances easily reached by train until after 2050. And while new aircraft engines are certainly more efficient than the old ones they replace, the environmental benefit is more than wiped out by the expansion in the number of flights.

An official strategy which not only wants to build a third runway at Heathrow but also expand regional airports is not going to rein in airline emissions – which raises the question of whether the government is serious about reducing the UK’s carbon emissions, let alone reaching net zero. And the plan to rely on international carbon offsets to balance the carbon books (as the legislation allows) is simply deceitful. Carbon offsetting will not deliver the net zero future that the science tells us we need to achieve, since all sectors in all countries will need to get as close as possible to zero emissions, and there’s a limit to how much remaining CO2 we can hope to soak up with new forests.

The truth is that aviation growth and our expectation of cheap flights cannot continue. The draft aviation strategy is an opportunity to address this, starting with a commitment to ensuring aviation makes a fair contribution to actual reductions in UK carbon emissions.

That means capping aviation emissions at current levels as a first step, cancelling plans for airport expansion, and investing in alternatives so that short- to medium-distance travel by train become attractive and affordable for all.

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This is not only a carbon emissions issue. The unsustainable growth in demand for flights is being driven to a significant extent by a minority of wealthy individuals, raising the issue of inequality and fairness too.

About 70% of flights are taken by just 15% of the population, and most people don’t fly at all in any given year. It’s not families taking an occasional holiday or business travellers who are fuelling the growth in demand for flying – it’s a small minority of wealthy individuals taking multiple flights a year.

Yet the harms caused by aviation growth, from noise and air pollution to habitat destruction as airports expand, is felt disproportionately by the less well-off. That’s why policies like the frequent flyer levy must be front and centre of the new aviation strategy, so that social justice and environmental protection go hand in hand.

The EU’s transport commissioner Violeta Bulc told airline CEOs this month that the aviation industry’s licence for growth would in future be linked directly to perceptions of sustainability.

Heathrow’s owners – and the government – need to read that memo too.

• Caroline Lucas is the Green party MP for Brighton Pavilion