
Travel Search - Limited usage.
Amadeus for Developers API is a free Transportation API that requires OAuth authentication, is served over HTTPS and has unconfirmed CORS support.
Discover Amadeus travel APIs and connect to the flight search, flight booking, hotel and destination content APIs that power the biggest names in travel.
Details from developers.amadeus.com.

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.
Predictive port congestion, ETA delay and freight volatility signals for 16 global ports
Geospatial data for Mexico City public transport system (Metro, Metrobús, Cablebús, RTP, etc.)
Screen any ship by IMO for OFAC/EU/UN/UK sanctions, ownership opacity and a vetting grade
The Amadeus for Developers API is provided by Amadeus IT Group SA (developers.amadeus.com). Discover Amadeus travel APIs and connect to the flight search, flight booking, hotel and destination content APIs that power the biggest names in travel.
Yes. The Amadeus for Developers 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 Amadeus for Developers API uses OAuth authentication, so you need to register for credentials before making requests.
CORS support for the Amadeus for Developers API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Amadeus for Developers API is served over HTTPS, so it's safe to use in production.