Picture one morning flight from Heathrow to Paris. 180 seats, 150 passengers, about 3 tonnes of jet fuel burned. Everything in this course is on that one plane. This lesson takes it apart, chapter by chapter, and says nothing about whether it should fly. That part is not the course's.
Three tanks the flight draws on. Tap the one that is never refilled on a human clock.
Tap the part of the picture that answers it.
The oil the fuel came from
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The air's room for carbon
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The quiet over the houses
The oil the fuel came from
Right. Lesson 2. Oil has no tap on a human clock; every tonne burned is a tonne out of a tank that is not refilling. The waste-made or clean-power share of the UK's fuel is the only part that came from a tap, and this one plane may carry none of it.
The air's room for carbon
Not yet. Lesson 4. The air is a tank with a line and the line is crossed, but the tonne does come back out, over centuries, through the sea and the plants. Slow, not never.
The quiet over the houses
Not yet. Lesson 5. The quiet comes back the moment the plane has passed. Its tap is instant; the cost is that it is taken many times a day.
A permit a tonneabout £50
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Noise, NOxat the gate
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Passenger duty£13 each
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The fuel rule2 in 100, UK-wide
The main bills, from chapter 2. A permit for every tonne, Paris being in the UK scheme: nearer £50 in 2025. A noise charge on take-off and landing, by category; £19.90 a kilogram of nitrogen oxide on landing. Passenger duty, £13 each to Paris. The fuel rule: 2 in 100 of UK jet fuel from waste or clean power.
3 tonnes
↓→
× 3.15
The flight burned about 3 tonnes of jet fuel. The UK scheme's factor is 3.15. About how many tonnes of carbon dioxide is that?
tonnes
Right. About 9.5 tonnes, on the fuel the airline records. At nearer £50 a permit, up to about £470 of carbon bill on this one flight. In 2025 part of it was still covered by permits the airline was given free; from 2026 it buys them all. On top: the noise and NOx charges and 150 lots of £13.
Each card is a bill on this flight. Is it a price, a cap, or a rule?
One card at a time. Tap the pile it belongs to.
Card 1 of 6
Air Passenger Duty, £13 a passenger to Paris
A permit for each tonne, bought in the UK scheme
2 in 100 of all UK jet fuel sold that year must be from waste or clean power
£19.90 for every kilogram of nitrogen oxide on landing
A noise charge on every take-off and landing, by the plane's category
The UK's law: net emissions 100 in 100 below 1990 by 2050
Air Passenger Duty, £13 a passenger to Paris → A price
Not yet. A price, collected as a tax. The seat is still allowed; it costs £13 more, paid to the government.
A permit for each tonne, bought in the UK scheme → A cap
Not yet. A cap. The number of permits is fixed and falls; the £50 came out of the trading, not out of a law.
2 in 100 of all UK jet fuel sold that year must be from waste or clean power → A rule
Not yet. A rule, on the fuel sellers, across everything they sell. They may pay a set fee instead. It says nothing about this one plane's share.
£19.90 for every kilogram of nitrogen oxide on landing → A price
Not yet. A price, kept by the airport as a charge. A cleaner engine pays less; a dirtier one is still allowed to land.
A noise charge on every take-off and landing, by the plane's category → A price
Not yet. A price. Heathrow's bill for the quiet it takes from the houses, paid by the airline and set by how loud the plane is.
The UK's law: net emissions 100 in 100 below 1990 by 2050 → A rule
Not yet. A rule, for the whole country. It sets no price and prints no permit; the other bills are how the country tries to reach it.
3Price
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1Cap
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2Rule
Right. Three prices, one cap, two rules: the main bills on one flight. Heathrow also charges 4p a kilogram of carbon on landing, a fourth price. None of them undoes the 9.5 tonnes. A bill attaches a cost to a drain; it does not refill the tank.
scope 1The airline
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scope 3Heathrow
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counts from 2033The UK's total
The count, from chapter 3. About 9.5 tonnes. The airline counts them as scope 1. Heathrow counts the same tonnes as scope 3, inside its 95 in 100. The UK's border count has kept international flights outside its total; from the 2033 to 2037 budget they count. Per passenger: 9.5 tonnes over 150 people is about 63 kilograms each.
Set how full the plane is and whether the high-altitude effect is in the factor. The exhaust is fixed at about 9,450 kilograms; only the division changes.
This setting105 kg a passenger
Full plane, ground factor52 kg a passenger
Passengers: 90 · High-altitude effect counted: No
90 passengers, without the high-altitude effect: about 105 kg each.
180 passengers, with the high-altitude effect: about 89 kg each of carbon dioxide equivalent.
What moves the per-passenger number, and what does it do to the exhaust?
Only the factor. The exhaust is the exhaust.
Not yet. True of the exhaust, and the per-passenger figure is the one that gets printed on a ticket. Ninety passengers or 180 is the difference between 105 kg and 53.
Only the passengers. The factor is a technicality.
Not yet. A 70 in 100 uplift is a bigger move than going from 150 to 180 passengers. The factor is where half the course's counting lives.
Both controls move it: filling the plane halves it, the factor raises it by 70 in 100. Neither changes the exhaust.
Right. From 90 to 180 passengers the figure halves. The uplift multiplies it by 1.7. The 9,450 kilograms left the engines whatever the label says.
Move both controls.
Carbon neutral seatbanned in the EU, 2026
vsvs
PwClimited assurance
The check, from chapter 4. The airline could sell a seat as carbon neutral by buying a forest credit. From September 2026 the EU bans that claim; a Dutch court found KLM's version misleading in 2024. PwC read Heathrow's count of the flight's tonnes, with limited assurance. The permit count is lesson 9's sum: public factor, the airline's fuel figure.
Put the course's four questions in the order it asked them.
Tap them in the order they happen, first to last. Each tap gets a number.
The tank→The bill→The count→The check
Right. The tank, the bill, the count, the check. Each one needs the one before: you cannot bill a cost you have not noticed landing, count without saying whose count, or check a count that has no edges.
More flights
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Should it be built?
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How is each counted and billed?
A third runway at Heathrow would add flights. The course takes no side on it. Which question can the course answer?
Whether the runway is right.
Not yet. The course says how the counting and the paying work, and stops. Right is a decision about what matters most, and the course has no vote in it.
How each extra flight will be counted and billed, and what the bills do and do not cover.
Right. That is the whole course: the tank it draws on, the three kinds of bill, the edges of the count, the name of the checker. What to do with those facts is a decision, and it is yours.
That the bills make the extra flights harmless.
Not yet. A bill attaches a price to a drain. It does not refill the tank. Lesson 13: a subtraction on paper is only as real as the tonnes, and a permit is a price, not a removal.
Lesson complete
One flight draws on a tank, carries four bills, sits in three counts, and gets checked by someone outside.