Many planes with Pratt & Whitney GTF engines are stuck on the ground while the engines get fixed. Type in a fleet size and pick which older engine fills the gap. You get the same sums I used in the SMBC/JSA and Spirit briefs: CO2, CO2 plus other warming, and the change in other pollution. Each number says how sure we can be about it.
For the whole fleet, over the months you pick. Older planes burn 16% to 20% more fuel (the range the engine makers and industry have published). I add that to each plane's normal yearly fuel. Then I turn fuel into CO2: every 1 kg of fuel makes 3.16 kg of CO2 (IATA's number). "CO2e" then multiplies that up to include warming from clouds and NOx. It is a rough idea of the total warming, not a number any rule uses.
For one plane, for one take-off and landing. The numbers come straight from ICAO's official engine test list (version 32). I compare the grounded new engine (neo) with two older engines (ceo) that could fill in. Then I multiply by roughly how many take-offs and landings a plane does in a year. That is the only guess. The rest is what the official tests say.
Why I keep them apart: Part 1 is about climate cost, the kind of number a lessor or insurer uses to price risk. Part 2 is about dirty air around the airport (NOx, HC, CO and soot). That is a different problem, with different rules, so I show it in kilograms and don't mix it into CO2e. I never mix official numbers with guesses into one number without saying so.
What this tool guesses: that older planes (ceo) fly in place of the grounded ones, and burn more fuel and make more pollution.
What someone who manages lending risk told me really happened: in one group of planes hit by Spirit going bust, no older planes filled in. Instead, the airline, Pratt & Whitney and Spirit's administrators made a deal. Engines were used for the hours they had left. Repairs were booked in early for 2026 and 2027. The planes were leased to other airlines (if the engine did not have the metal fault) or taken apart. Other airlines took up the flying, so no older, thirstier planes were needed. The money hit came a different way: some planes came back worth less than their book value. That is a straight loss on paper, and it has nothing to do with the fuel and pollution this tool works out.
Some planes have also been taken apart earlier than normal. Spare GTF engines are in such demand that the engines alone can be worth more than the whole plane. So some planes were stripped for parts or sold, and the engines were leased out on their own. This does not happen most of the time, and every case is different. But it does happen, along with re-leasing and repairs.
Older planes filling in can still happen across a fleet this big. It just means this tool's guess is one possible outcome, not the only one. Which one wins (older planes, re-leasing, or taking planes apart) probably depends on the engine, how easy it is to get parts, and how strong each lessor's hand is in talks. There is no one pattern for everyone.
Normal fuel use per plane is my estimate. Nobody else has checked it yet.
Bars to the right mean more pollution than the new engine. Bars to the left mean less.