# Everything in the air over London

> Every transponder currently reporting inside the M25, and which way it is going.

- Category: Aviation
- Cadence: live
- Status: Live: values change continuously; cite the retrieval time.
- Dataset key: `live-aircraft`
- Source: [OpenSky](https://opensky-network.org/)
- Licence: OpenSky Network terms of use — [terms](https://opensky-network.org/about/terms-of-use)
- Canonical page: [https://londongraph.com/g/live-aircraft-over-london](https://londongraph.com/g/live-aircraft-over-london)
- Machine-readable record: [https://londongraph.com/data/live-aircraft-over-london](https://londongraph.com/data/live-aircraft-over-london)

## Methodology

ADS-B positions from the OpenSky Network, bounded to 51.25–51.70°N and 0.55°W–0.30°E. Aircraft are classed by vertical rate: descending faster than 2 m/s counts as arriving, climbing faster than 2 m/s as departing. Positions are proxied through an API route and cached for LIVE_CACHE_TTL seconds, so OpenSky is polled once per interval no matter how many people are watching. Coverage depends on volunteer receivers — this is what the network can see, not a guaranteed census of the sky.

## Visualisations

- [Map](https://londongraph.com/g/live-aircraft-over-london): Every transponder currently reporting inside the M25, and which way it is going.
- [Altitude](https://londongraph.com/g/live-aircraft-over-london?view=altitude): Show the distribution of reported barometric altitudes.
- [Flight phase](https://londongraph.com/g/live-aircraft-over-london?view=flight-phase): Separate aircraft that are descending, climbing, level or on the ground.

## Citation guidance

Attribute the original publisher named above and identify LondonGraph as the visualisation and methodology layer. Do not describe live values as a historical census, and do not present placeholder values as observations.