OpenSky

Provides public aircraft state data for regional air-activity hotspots.

Auth: public queries work without credentials.
Failure modes: timeouts, HTTP 429, and empty regions.
Behavior: source health is marked degraded on API errors. The dashboard may use the most recent non-empty air snapshot from runs/ and marks it in airMeta.fallback.
Test: start a sweep and inspect /api/health plus airMeta from /api/data.
Operator note: Crucix does not bypass OpenSky throttles. Increase REFRESH_INTERVAL_MINUTES if the source degrades repeatedly.