Carbon Sky Index ingests raw ADS-B (Automatic Dependent Surveillance–Broadcast) position observations which aggregates feeds from a global network

Raw position reports are not redistributed by CSI. Instead, they are processed through CSI's proprietary segmentation pipeline, which:

• Classifies aircraft by registration and type using FAA, EASA, and ICAO registries
• Filters business and private aviation movements from commercial, charter, cargo, and military traffic
• Segments continuous position reports into discrete flight records with origin, destination, duration, and distance
• Applies LTO (landing and take-off) and cruise emissions factors from the EUROCONTROL EMEP/EEA Air Pollutant Emission Inventory Guidebook 2023, calibrated across 160 aircraft types

The resulting flight database covers 22,581 business and private aircraft and is unique to CSI. All platform outputs — emissions calculations, spike detections, route aggregations, and event analyses — are derived from this processed dataset.

A raw ADS-B signal contains a Mode S ICAO 24-bit address which is a hexadecimal identifier, not a tail number. Resolving that hex code to a confirmed registration, aircraft type, and engine specification requires four steps:

1. Hex to registration: Mode S code matched against our registration database to retrieve the civil tail number
2. Registration to aircraft type: confirmed registration matched to manufacturer, model, and variant
3. Type to engine specification: aircraft type matched to engine type and LTO fuel flow rates from the ICAO Engine Emissions Databank
4. Engine count confirmation: engine count confirmed from type specification and applied to the LTO calculation

Raw ADS-B data is a continuous stream of position messages, not a list of flights. A confirmed flight event requires:

• Position messages showing transition from ground to airborne state at a known aerodrome
• Continuous signal confirming sustained climb
• A return to ground state at a destination aerodrome
• Flight meeting minimum distance and duration thresholds. Events below these thresholds are classified as ground movements or signal anomalies and excluded

Where origin or destination cannot be confirmed from ADS-B signal, the endpoint is recorded as unknown (UNK) rather than excluded. These flights appear in the database with partial routing information.

Where an aircraft's ADS-B signal drops mid-flight and is never recovered, for example, a transponder signal lost at cruise altitude with no subsequent detection at a destination, the flight is excluded from the published record. It cannot be confirmed as a completed flight.

Carbon Sky Index applies a conservative approach throughout flight detection: where there is ambiguity, we err toward undercounting rather than overcounting. This means some legitimate flights may be absent from our database due to coverage limitations, particularly in regions with lower receiver density.

Flight data on Carbon Sky Index is compiled from multiple flight data sources including ADS-B transponders. Carbon Sky Index endeavours to keep data as reliable as possible but gives no warranty and accepts no responsibility or liability for the accuracy or completeness of the information provided.