Ministers say they tackling one of the hardest sectors to decarbonise, but not everyone is on board with sustainable aviation fuel.
Guilt free flying is one step closer to reality, the government has said, as it awarded Virgin Atlantic up to £1m to test the first transatlantic commercial flight powered by green fuel.
A normal Boeing 787 passenger plane will next year jet from London to New York in a bid to prove long haul flights can be fuelled using only sustainable aviation fuel (SAF).
Environmentalists question the green credentials of SAF and argue the only guaranteed way to shrink the impact of flying is simply by doing it less.
But the government says this test flight will show "guilt-free flying" is on the horizon, as it plans for an increase in passengers.
"That will be the longest time that sustainable aviation fuels have been flown, and it will be... absolutely key in showing other airlines, the rest of the world what can be done," Aviation Minister Baroness Vere told Sky News.
Current rules only allow a maximum of 50% SAF blended with normal jet fuel, kerosene, to be used in commercial aircraft engines.
Virgin will be leading a consortium including Rolls-Royce, Boeing, Imperial College London.
They say the plane is sure to make it across the Atlantic safely because they have run test flights, though could not disclose the distances.
"The beauty about sustainable aviation fuel is it's a drop in fuel, which actually means it smells and looks exactly like jet fuel," Virgin CEO Shai Weiss said.
Speaking at Heathrow Terminal 3, Baroness Vere said the flight will "absolutely" be good for the environment because it will take the UK closer to net zero aviation, one of the hardest sectors to decarbonise.
How sustainable is sustainable aviation fuel?
The government expects this test flight to be fuelled "primarily" by waste oils and fats.
This would cut emissions by 70% compared with kerosene, because they are waste products and do not need extracting.
Virgin said the remaining 30% will effectively be removed using biochar, a material that can trap and store the equivalent amount of carbon from the atmosphere.
But the government's own climate advisers, the Climate Change Committee (CCC), have warned against over reliance on SAF.
The CCC's head of net zero, David Joffe said: "It's easy to get carried away in the same way that people are getting carried away with the [nuclear] fusion announcement... and say, 'oh it's about to break through, therefore we don't need to do anything [to reduce demand]'".
"But our analysis suggests that even by 2050, there just won't be enough SAF to do everything."
Baroness Vere said: "I am confident the sustainable aviation fuels are sustainable, but... we need to look very carefully [at] the feedstocks."
She added: "That's why we need to invest now to bring forward the R&D [research and development] that will make those pathways happen."
'Really worrying' the government won't cut demand
The government is banking on SAF to help offset its planned 70% boom in passengers. The expansion flies in the face of warnings from the CCC that an increase of no more than 25% is possible while still meeting climate goals.
The minister shot down calls for a levy on frequent fliers, which would allow everyone to take one or two trips a year and then tax each flight incrementally after that.
"This government is anti-aviation emissions, not anti-flying," she said. "We can continue to fly because it's good for our economy, it's good for our friendships and seeing our family."
Alethea Warrington from climate charity Possible called it "really worrying that the government is refusing to put in place any measures to limit demand for flights".
There is going to be "a huge increase in emissions that most people in the UK are not going to benefit from", she added.
In the UK, 70% of flights are made by 15% of the population, with 52% not flying abroad at all.
What is sustainable aviation fuel?
Sustainable aviation fuel can be made from waste products like cooking oil or black binbag rubbish. That means lifecycle emissions are 70% lower because they don't need extracting from the ground, like normal jet fuel.
But emissions when they are burned in a jet engine are the same, and there are concerns that there is not an endless supply of waste.
SAF can also be made from plants. This form too causes the same emissions as kerosene when burned, but these in theory can be sucked up again by the new plants when they grow.
This form of SAF is particularly contentious because of concerns about monocultures being bad for life-sustaining ecosystems, and because of the land it would need. It is also hard to guarantee the new crops will absorb the equivalent emissions.
A third form involves creating hydrogen from renewable energy and combining it with carbon dioxide captured from the air, but it is very energy intensive.
Original source: Sky News