Aircraft valuations, FAA registry lookups, cost of ownership and aviation market data.
Windsock API is a free Transportation API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from windsock.ai.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Community maintained, developer-friendly public transport API
The Windsock API is provided by Windsock (windsock.ai).
Yes. The Windsock API is listed in the Transportation category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The Windsock API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Windsock API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Windsock API is served over HTTPS, so it's safe to use in production.