IATA RP 1726
Ask three flight-emissions calculators for the carbon footprint of the same seat on the same route and you will usually get three different numbers — sometimes differing by more than a factor of two. The divergence comes from incompatible choices: different fuel-burn assumptions, different load factors, different ways of splitting a flight’s emissions between passengers and cargo, and different ways of weighting a business seat against an economy seat. IATA RP 1726 is the aviation industry’s answer to that confusion: a single, weight-based, industry-developed methodology for allocating a flight’s CO2 to individual passengers by cabin class.
Adopted by IATA’s Passenger Services Conference in March 2022, RP 1726 is the methodology underneath IATA’s CO2 Connect calculator and a growing share of corporate travel reporting. This reference covers the full standard: the six-step weight-based allocation chain, the 3.16 combustion factor and its well-to-wheel variant, cabin-class weighting, passenger-versus-cargo allocation, the previous-calendar-year averaging rule, the deliberately narrow CO2-only scope, SAF and offset treatment, and how an RP 1726 result maps onto airline Scope 1 and traveller Scope 3 reporting.
IATA RP 1726 is the air transport industry's recommended practice for per-passenger CO2. It takes a flight's fuel burn, subtracts the belly-cargo share, allocates the rest across cabin classes, and converts at 3.16 kg CO2 per kg of jet fuel.
1. What IATA RP 1726 Is
IATA Recommended Practice 1726, the Passenger CO2 Calculation Methodology, was developed by an industry working group of airlines, aircraft manufacturers, and standard-setting bodies, and adopted by IATA’s Passenger Services Conference in March 2022. It is the first industry-agreed method for allocating a flight’s carbon dioxide emissions to individual passengers on a consistent, weight-based basis.
The problem it addresses is proliferation. Travellers, corporate travel managers, and travel agents increasingly demand a per-flight CO2 figure, but the market filled with calculators that each made different assumptions and produced different answers — denting confidence and making any two numbers impossible to compare. RP 1726 establishes one defined scope, one fuel-to-CO2 conversion factor, one cabin-class weighting principle, and one allocation logic, so that results calculated by different parties on the same activity are genuinely comparable.
Two properties define its character. First, it is voluntary: a recommended practice, not a mandatory standard, that any airline, agent, or organisation may adopt. Second, it is most accurate with primary data: the methodology is built to run on verified airline operational data — actual aircraft-specific fuel consumption and airline-specific load factors — rather than generic industry averages, and it is least reliable when forced onto modelled assumptions. This is the design philosophy that distinguishes it from earlier, model-only calculators.
RP 1726 calculates passenger CO2 only. It is an allocation methodology — how a flight’s emissions are divided among the people on board — not an emission-factor database for routes or a whole-of-flight environmental assessment. Its companion, RP 1678, performs the equivalent job for air cargo, and the two are designed to allocate a single flight’s emissions between passengers and freight without overlap.
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2. Scope and Boundary
RP 1726 confines its calculation scope strictly to the fuel burn and CO2 emissions related to flight operations. That boundary is deliberate and narrower than many users assume — and understanding what sits inside it, what is optional, and what is excluded is essential before citing an RP 1726 number.
| Included by default | Optional add-on | Excluded |
|---|---|---|
| CO2 from jet fuel combustion in flight (tank-to-wheel) | Upstream well-to-tank CO2 of fuel production/transport (where local regulation requires) | Vehicle/aircraft manufacture and infrastructure |
| Per-passenger allocation by cabin class | Non-CO2 and non-aircraft emissions / Radiative Forcing Index (displayable, not recommended) | Airport ground operations beyond flight fuel burn |
| Passenger-versus-cargo split | SAF reduction applied to the result | Contrails and other non-CO2 warming effects by default |
The default boundary is tank-to-wheel: the CO2 produced by burning the fuel in flight. The methodology gives flexibility to add the upstream well-to-tank component — the emissions of producing and transporting the jet fuel — where local regulation requires it, using the well-to-wheel variant of the conversion factor. Any optional inclusion must be clearly flagged to the consumer of the data so that an RP 1726 figure is never silently broader than its default scope.
3. The Six-Step Calculation Chain
RP 1726 reduces per-passenger CO2 to a repeatable weight-based sequence. The principle is that fuel is allocated in proportion to the weight each element contributes to the aircraft, and passengers then receive their share weighted by cabin class.
Determine the total fuel burned on the flight (or leg), preferably from the airline’s actual measured fuel data averaged over a representative period, not a single flight.
Sum the weight of passengers (actual or the standard weight) and the weight of belly cargo and mail, excluding the tare weight of pallets and containers that are not payload.
Allocate fuel by weight share: the passenger fuel is the total fuel multiplied by the passenger weight divided by the total payload weight. The remainder is attributed to belly cargo (handled under RP 1678).
Divide the passenger fuel by the number of passengers carried to get an average fuel burn per passenger for the period.
Weight the per-passenger fuel by cabin class, so a premium seat — occupying more weight and space — carries proportionally more fuel than an economy seat (see section 5).
Multiply the cabin-class-weighted fuel burn per passenger by the CO2 emission factor of 3.16 kg CO2 per kg of jet fuel to get per-passenger CO2 (or 3.84 for the well-to-wheel CO2e variant).
Suppose a leg burns 10,000 kg of fuel; total payload is 12,000 kg, of which passengers account for 9,000 kg and belly cargo 3,000 kg. Passenger fuel = 10,000 × (9,000 ÷ 12,000) = 7,500 kg. With 150 passengers, average fuel per passenger = 7,500 ÷ 150 = 50 kg. An economy seat at the baseline weighting therefore emits 50 × 3.16 = 158 kg CO2; on the well-to-wheel variant, 50 × 3.84 = 192 kg CO2e. The cabin-class step would scale a premium seat above this baseline. All inputs here are stated illustrative figures — they are not airline-specific data and must not be reused as factors. Real results require verified airline fuel and load-factor data.
4. The 3.16 Emission Factor (and 3.84 Well-to-Wheel)
The conversion from fuel mass to CO2 rests on a physical constant. Burning one kilogram of jet kerosene produces a fixed mass of CO2 determined by the fuel’s carbon content — internationally recognised as 3.16 kg CO2 per kg of fuel. RP 1726 uses this factor, and it is the same value used under CORSIA, which keeps the methodology aligned with the international aviation offsetting scheme.
The two factors answer different questions. The 3.16 factor counts only the CO2 released by combustion in flight — the default RP 1726 boundary. The 3.84 factor is the well-to-wheel CO2e equivalent, adding the upstream emissions of producing and transporting the fuel; it is used when the optional well-to-tank component is included, typically to satisfy a local regulatory requirement. The gap between them is the upstream fuel cycle made visible, not a different physical combustion.
Do not mix the two factors within one dataset without labelling. A per-passenger figure built on 3.16 is tank-to-wheel; one built on 3.84 is well-to-wheel and roughly 22% higher for the same fuel burn. Comparing a 3.16 result against a 3.84 result and reading the difference as an efficiency change is a boundary error, not a real reduction or increase.
5. Cabin-Class Weighting
A flat per-passenger average would treat every seat as equal, but seats are not equal. A premium seat occupies more floor area and adds more weight per passenger than an economy seat, so it is responsible for a larger share of the aircraft’s fuel burn. RP 1726 corrects for this with cabin-class weighting factors applied across the standard travel classes.
| Cabin class | Code | Relative weighting direction |
|---|---|---|
| Economy | Y | Baseline — lowest weighting per passenger |
| Premium economy | W | Above economy |
| Business | J | Substantially above economy |
| First | F | Highest weighting per passenger |
The weighting reflects the weight and space each class occupies, with separate factor sets for narrow-body and wide-body aircraft. IATA publishes specific multipliers within the methodology; the direction is invariant — economy is the baseline and premium classes carry progressively more — but the exact factors are an IATA-published table that should be taken from the current RP 1726 document rather than memorised. Members with seating configurations that differ from the standard may use their own cabin-class factors where these better reflect the weight and space of a given class, provided the basis is disclosed.
The cabin-class weighting is why a business-class footprint is several times an economy footprint on the same route. When reporting corporate travel, applying RP 1726 cabin-class weighting rather than a flat per-seat average materially changes the result for premium-heavy travel programmes — and is the methodologically correct treatment.
6. Passenger vs Belly-Cargo Allocation
On most passenger flights the aircraft also carries belly cargo and mail, and a flight’s fuel must be split fairly between the people and the freight so that neither side double-counts nor drops emissions. RP 1726 allocates by weight: the passenger share of fuel is proportional to the passenger weight as a fraction of total payload, with the remainder assigned to cargo.
The cargo side is then handled by IATA RP 1678, the cargo CO2 methodology, which uses the same 3.16 combustion factor and the same weight-based principle to derive a leg-based emission factor in kg CO2 per kg of payload. The two recommended practices are deliberately harmonised so that the passenger allocation under RP 1726 and the cargo allocation under RP 1678 sum to the flight’s total without overlap. For freight that connects into a wider multimodal chain, the cargo result feeds into broader transport-chain accounting under the GLEC Framework.
A subtle asymmetry: if the passenger cabin is underutilised, the weight-based split shifts more of the flight’s CO2 onto cargo, even though cargo cannot influence passenger load. This is a known limitation IATA continues to explore. When reporting, disclose the load-factor basis so a reader can interpret an unusually high or low per-passenger figure.
7. Averaging Logic — Why Not Single-Flight Data
One of the most misunderstood features of RP 1726 is its insistence on averages rather than single-flight figures. The methodology explicitly recommends against using individual, single-flight data to predict a flight’s CO2.
Factors beyond a member’s control — weather, traffic, seasonality, directionality — make single-flight fuel burn an unreliable predictor; the recommended basis is an average over a representative period, typically the previous calendar year.
— principle of IATA RP 1726The rationale is statistical. A single flight’s fuel burn is shaped by transient conditions that have nothing to do with the route’s structural efficiency: a headwind, an air-traffic-control hold, a seasonal load swing. Averaging over a representative period — the previous calendar year is the recommended range — smooths these out and yields a figure that genuinely represents the route and aircraft, which is what a passenger or corporate reporter needs. Data is re-audited each calendar year, or whenever a new fuel dataset is adopted.
8. Data Quality and the ICAO Divergence
RP 1726’s accuracy is a direct function of the data fed into it. The methodology is designed to run on verified, airline-specific operational data and is least reliable on generic industry averages. This is also the source of a frequently observed divergence between IATA RP 1726 results and ICAO calculator results.
| Dimension | IATA RP 1726 (with airline data) | ICAO-style modelled calculators |
|---|---|---|
| Fuel burn | Actual airline-measured fuel data | Modelled fuel burn |
| Load factor | Airline-specific actual load factors | Global average load factor |
| Cabin-class treatment | Weight/space-based weighting factors | Varies; often coarser |
| Typical result direction | Often higher — reflects real, lower-than-average utilisation on many flights | Often lower — global-average load factor flatters per-passenger figures |
| Best for | Airline-specific, defensible per-passenger reporting | Quick generic estimates without airline data |
The practical consequence is that RP 1726 with airline data often returns higher per-passenger CO2 than a global-average model — not because it is pessimistic, but because the global-average load factor used by modelled calculators is often higher than the actual load factor of a given flight, which flatters the per-passenger figure. A reporter switching from a modelled calculator to RP 1726 should expect the number to move and should attribute that move to the data basis, not to a change in the underlying flying.
9. SAF and Carbon Offsets
RP 1726 includes guidance on sustainable aviation fuel (SAF) and carbon offsets, recognising that both increasingly feature in how the industry reports and reduces aviation CO2. Where an airline has purchased SAF and used it on flights carrying passengers, the methodology allows the corresponding emissions reduction to be reflected, subject to greenhouse-gas-accounting protections against double counting.
The allocation principle ties to who claims the reduction. Reductions can be reported by members and third parties as part of their Scope 1 and Scope 3 emissions respectively, in accordance with the GHG Protocol — the airline claiming within its own operational footprint and the traveller or corporate within their value chain. Carbon offsets are treated as a separate layer applied after the CO2 calculation, not as a reduction in the calculated emissions themselves. The interaction with the broader aviation offsetting scheme is governed by CORSIA, with which the 3.16 factor is aligned.
10. Non-CO2 Effects, RFI and Contrails
This is the most consequential boundary in the standard and the one most often misrepresented. Aviation’s climate impact is not only CO2 — contrails, nitrogen oxides, and other non-CO2 effects contribute additional warming, often expressed through a Radiative Forcing Index (RFI). RP 1726 confines its calculation to CO2 from fuel burn and does not recommend incorporating non-CO2 or non-aircraft effects or RFI into the headline figure.
The methodology does provide flexibility: a user may display non-CO2 and non-aircraft emissions and RFI, provided they clearly indicate that these were included. The deliberate default is CO2-only because the science of quantifying non-CO2 effects at the per-flight level remains uncertain and methodologically contested, and IATA’s position is that specific guidance will be added once industry consensus exists.
An RP 1726 figure understates aviation’s total climate impact because it excludes non-CO2 warming by default. This is a known, disclosed limitation, not a flaw to hide. When citing an RP 1726 number for a climate-impact claim, state that it is CO2-only; do not silently present it as the full warming effect of a flight, and do not apply an RFI multiplier to an RP 1726 figure without flagging that you have departed from the standard’s default.
11. RP 1726 vs Other Air-Travel Methodologies
Practitioners reporting flight emissions choose between several methodologies. The right choice depends on whether airline-specific data is available and what the number is for.
| Dimension | IATA RP 1726 | ICAO calculator | DEFRA factors |
|---|---|---|---|
| Type | Allocation methodology | Modelled calculator | Published distance-band factors |
| Data basis | Actual airline fuel + load factors | Global-average modelled | Average factors by haul/class |
| Cabin class | Weight/space weighting | Coarser class treatment | Class multipliers by haul |
| Boundary | CO2, TTW default (WTW optional) | CO2, varies | CO2e incl. WTT and RF uplift option |
| Best use | Airline-specific, defensible reporting | Quick generic estimate | Corporate Scope 3 where no airline data |
The methodologies are not mutually exclusive in practice. An airline reporting its own footprint, or a travel platform with access to verified carrier data, uses RP 1726; a corporate reporter without airline data commonly falls back on published DEFRA emission factors by haul and class, which is the basis the live business travel air calculator applies. The key discipline is to disclose which methodology produced a figure and not to compare numbers across methodologies as if they were like-for-like.
12. IATA CO2 Connect — the Operational Implementation
RP 1726 is the methodology; IATA CO2 Connect is its principal operational implementation. CO2 Connect is IATA’s calculation engine, powered by RP 1726, that uses real operational data submitted by airlines — aircraft-specific fuel consumption and airline-specific load factors — rather than industry averages, to produce per-passenger and per-shipment CO2 figures.
The relationship matters for interpreting any CO2 Connect output: the methodology guarantees the calculation logic, and the airline-contributed data drives the accuracy. The engine’s data model runs from origin and destination airports, flying time, aircraft type, and airline-specific seat capacity and occupancy, subtracts belly cargo, and applies the cabin-class factor to yield per-passenger CO2. For cargo, the companion CO2 Connect for Cargo applies RP 1678 and is positioned as aligned with broader transport standards including ISO 14083 and the GLEC Framework.
When a vendor states a flight figure is “RP 1726-based,” ask whether it uses verified airline data or modelled averages. Both can be RP 1726-compliant in their calculation logic, but only the airline-data version delivers the accuracy the methodology was designed for. The methodology label alone does not guarantee the data quality.
13. Mapping to Corporate GHG Inventory
An RP 1726 per-passenger figure lands in different places depending on who is reporting. The same physical flight emission is an operational emission for the airline and a value-chain emission for the traveller’s organisation.
Airline — Scope 1
For the operating airline, the fuel burned is a direct emission from owned or controlled aircraft, reported in Scope 1. RP 1726 governs how that total is allocated to passengers, not whether it is the airline’s direct emission.
Corporate traveller — Scope 3 Category 6
For an organisation whose employees fly, the per-passenger figure is a Scope 3 Category 6 business-travel emission. RP 1726 supplies a defensible per-traveller number where airline data is available.
The accounting parallel to the SAF and offset rules in section 9 holds here: the airline claims reductions in Scope 1, the traveller’s organisation in Scope 3, and the GHG-accounting double-counting protections keep a single tonne of avoided CO2 from being claimed twice. For corporate travel programmes, this places RP 1726 alongside the GHG Protocol Scope 3 Standard, which governs how the business-travel category is defined and disclosed, and expressed in CO2e terms when aggregated with other gases.
14. Double-Counting Protections
Because the same flight emission can be reported by the airline and by every passenger’s organisation, RP 1726 is explicit about double-counting protections. The protections are not about the emission itself — the airline’s Scope 1 and the traveller’s Scope 3 are different views of the same tonne and are both legitimate — but about reductions and claims.
The rule is that a SAF-driven or offset reduction is claimed once, by one party, in the appropriate scope: the airline in Scope 1 or the traveller’s organisation in Scope 3, consistent with the GHG Protocol, but not both for the same reduction. This keeps the aggregate honest when an airline and its corporate customers both report on the same flights. A reporter relying on an RP 1726 figure should confirm whether any embedded SAF or offset reduction has already been claimed upstream before claiming it again.
15. Common Misconceptions
Six recurring errors appear in how RP 1726 figures are calculated and cited:
16. Implementation Checklist
A practical sequence for an organisation adopting RP 1726 for per-passenger CO2 reporting:
17. Limitations and Edge Cases
RP 1726 is the strongest available per-passenger CO2 methodology, but it carries boundaries practitioners should disclose.
- CO2-only by default. Non-CO2 warming — contrails, NOx — is excluded unless optionally and explicitly displayed, so the headline figure understates total climate impact.
- Accuracy depends on data. Run on modelled averages rather than verified airline data, RP 1726 loses much of its advantage; the methodology label alone does not guarantee a good number.
- Cabin under-utilisation shifts CO2 to cargo. The weight-based split can load more emission onto freight when the passenger cabin is empty, a known asymmetry under industry review.
- Cabin-class factors are configuration-sensitive. Standard multipliers may not fit unusual seating; members may substitute their own factors, which preserves accuracy but reduces cross-airline comparability unless disclosed.
- Voluntary, not mandated. Adoption is a choice; absent a regulatory mandate, different reporters may still use different methodologies, so disclosure of which one was used remains essential.
18. Frequently Asked Questions
IATA RP 1726 is the air transport industry’s Recommended Practice for calculating per-passenger CO2 emissions, adopted by IATA’s Passenger Services Conference in March 2022. It allocates a flight’s CO2 to individual passengers on a weight basis, splits emissions between passengers and belly cargo, applies cabin-class weighting, and converts fuel to CO2 using a factor of 3.16 kg CO2 per kg of jet fuel. It is voluntary and most accurate with verified airline operational data.
3.16 is the internationally recognised constant for the mass of CO2 produced by burning one kilogram of jet fuel — the tank-to-wheel combustion factor RP 1726 uses by default, aligned with CORSIA. A well-to-wheel variant of 3.84 kg CO2e per kg of fuel adds the upstream emissions of producing and transporting the fuel and is used when the optional well-to-tank component is included.
No, not by default. RP 1726 confines its scope to CO2 from fuel burn and does not recommend incorporating non-CO2 effects, contrails, or a Radiative Forcing Index into the headline figure. A user may optionally display non-CO2 and RFI values provided they clearly indicate these were included. Because of this, an RP 1726 figure understates aviation’s total climate impact and should be cited as CO2-only.
Premium seats occupy more weight and space per passenger, so RP 1726 applies cabin-class weighting factors that scale a seat’s share of fuel above the economy baseline — economy (Y) lowest, then premium economy (W), business (J), and first (F) highest — with separate factor sets for narrow-body and wide-body aircraft. The exact multipliers are published in the RP 1726 document; airlines with non-standard configurations may use their own factors if disclosed.
Single-flight fuel burn is distorted by factors outside an airline’s control — weather, air-traffic delays, seasonality, and directionality. RP 1726 therefore recommends averaging fuel and load data over a representative period, typically the previous calendar year, to produce a figure that represents the route and aircraft rather than the conditions of one particular day.
RP 1726 used with airline data applies actual fuel burn and airline-specific load factors, while ICAO-style calculators typically use modelled fuel burn and a global-average load factor. Because the global average is often higher than a given flight’s actual load factor, modelled calculators tend to produce lower per-passenger figures. The difference reflects the data basis, not a change in the underlying flying.
RP 1726 handles passenger CO2; RP 1678 handles air cargo CO2 using the same 3.16 factor and weight-based principle, so the two split a flight’s emissions without overlap. IATA CO2 Connect is the operational calculation engine that implements RP 1726 (and RP 1678 for cargo) using verified airline operational data rather than industry averages.
For the operating airline, the flight fuel is a Scope 1 direct emission and RP 1726 governs how it is allocated to passengers. For an organisation whose employees fly, the per-passenger figure is a Scope 3 Category 6 business-travel emission. Double-counting protections ensure SAF or offset reductions are claimed once, by one party, in the appropriate scope under the GHG Protocol.
RP 1726 is the allocation methodology; the factors and disclosure come from the surrounding cluster. Pair it with CORSIA for the aligned 3.16 factor and offsetting context, and the GHG Protocol Scope 3 Standard for Category 6 placement. Where verified airline data is unavailable, the business travel air calculator applies published DEFRA distance-band factors as a defensible fallback.