# RunwayFacts — Global Airport & Runway Facts, Rankings & Knowledge Graph

> RunwayFacts provides verified, structured physical aerodrome specifications, runway inventories, dimensional rankings, and Haversine spatial comparative graphs for 650 international commercial airports across 165 countries.

## Statistical Framework & Ranking Universes
- **Universe A: RunwayFacts Published Dataset (n=650)**: Curated high-confidence commercial aerodromes meeting strict criteria (paved runways ≥3,000 ft, validated IATA/ICAO codes).
- **Universe B: Global Commercial Ranking Universe (n=7,558)**: Broader statistical universe of all commercial facilities in OurAirports database used for percentile calculations and global ranks.
- **Universe C: Country Commercial Universe**: National subset of qualifying commercial aerodromes within each sovereign territory (e.g. n=2,020 in United States, n=264 in China).

## Core Knowledge Graph & Entity Model
- **Primary Entity**: Airport Aerodrome (identified by IATA 3-letter code or ICAO 4-letter ident)
- **Key Attributes**:
  - `runways`: Full inventory of active/closed physical runways, lengths (ft/m), widths, surface composition, lighting flags, magnetic designations (le_ident/he_ident).
  - `rankings`: Explicitly partitioned between Published Dataset Rank, Global Commercial Universe Rank (with percentiles), and National Rank.
  - `nearby_constraint_matches`: Precomputed comparative aerodromes within 100 NM radius meeting minimum 5,000 ft paved criteria.
  - `provenance`: Traceable data lineage from OurAirports open aviation records (Snapshot 2026-09-01, SHA-256 verified).

## Machine-Readable API Endpoints
- Single Airport Entity: `https://runwayfacts.com/api/airport/{iata}.json` (e.g. `https://runwayfacts.com/api/airport/den.json`)
- Sitemap (Full Index): `https://runwayfacts.com/sitemap.xml`
- Global Aerodrome Index: `https://runwayfacts.com/airports/`
- Country Hubs: `https://runwayfacts.com/countries/` (e.g. `https://runwayfacts.com/country/us/`)
- Records & Extremes: `https://runwayfacts.com/records/longest-runways/`, `https://runwayfacts.com/records/highest-airports/`

## Usage & Operational Safety Notice
RunwayFacts data is compiled for statistical, research, and comparative reference only. NOT FOR FLIGHT PLANNING OR REAL-TIME OPERATIONAL AVIATION USE. Always consult official AIP/NOTAMs.