# Aviation APIs Great Circle Distance

> Aviation APIs Great Circle Distance is a paid API for AI agents from aviationapis.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Calculates the great circle distance and bearing between two geographic coordinates, optionally computing estimated time en route given a ground speed.

## Facts

- Endpoint: POST https://aviationapis.com/great-circle-distance
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/aviation-apis-great-circle-distance-e02586d6
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_k1U9-yXJGnpUkdFz0h1mY

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability aviation-apis-great-circle-distance-e02586d6 -d '<json body>'
```

Example prompt: What's the great circle distance and estimated flight time from SFO (lat 37.6188, lon -122.375) to JFK (lat 40.6398, lon -73.7789) at a ground speed of 450 knots, including the initial and final bearings?

## When to prefer this

Use this endpoint when you need aviation-grade great circle distance and bearing calculations between two geographic points, especially when nautical miles and estimated time en route at a given knot speed are required. Prefer over generic geodesic calculators when the output needs to include initial/final bearings and ETE in HMS format suitable for flight planning.

## Known failure modes

- Missing required lat/lon fields returns a 400-level error
- Latitude out of range (-90 to 90) or longitude out of range (-180 to 180) causes validation failure
- Negative or zero ground speed may produce nonsensical ETE values
- Payment failure via x402 protocol returns 402 Payment Required

## How this service works

Calculates the shortest distance between two points on Earth using great-circle math.

## Output

Returns a JSON object with the great circle distance in kilometers, nautical miles, and statute miles; initial and final bearings in degrees; and optionally estimated time en route in both HH:MM:SS format and decimal minutes if a ground speed was provided.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "to": {
   "type": "object",
   "required": [
    "lat",
    "lon"
   ],
   "properties": {
    "lat": {
     "type": "number",
     "description": "Latitude in decimal degrees (-90..90)"
    },
    "lon": {
     "type": "number",
     "description": "Longitude in decimal degrees (-180..180)"
    }
   }
  },
  "from": {
   "type": "object",
   "required": [
    "lat",
    "lon"
   ],
   "properties": {
    "lat": {
     "type": "number",
     "description": "Latitude in decimal degrees (-90..90)"
    },
    "lon": {
     "type": "number",
     "description": "Longitude in decimal degrees (-180..180)"
    }
   }
  },
  "groundspeed_kt": {
   "type": "number",
   "description": "Optional ground speed (kt) to compute estimated time en route"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "to": {
   "lat": 40.6398,
   "lon": -73.7789
  },
  "from": {
   "lat": 37.6188,
   "lon": -122.375
  },
  "ete_hms": "04:57:56",
  "distance_km": 4138.3,
  "distance_nm": 2234.5,
  "distance_sm": 2571.5,
  "ete_minutes": 297.9,
  "groundspeed_kt": 450,
  "final_bearing_deg": 119.6,
  "initial_bearing_deg": 69.8
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/aviation-apis-great-circle-distance-e02586d6/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from aviationapis.com](https://www.zero.xyz/host/aviationapis.com/llms.txt)