AviationAPI
FAA Aeronautical Charts and Publications, Airport Information, and Airport Weather
Access traffic data from the ADOT API.
AZ511 API is a free Transportation API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from az511.com.

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Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
FAA Aeronautical Charts and Publications, Airport Information, and Airport Weather
164,068 aircraft accident narratives from 128 official investigation authorities, plus FAA data
Sailing times and capacities for BC Ferries
Screen any ship by IMO for OFAC/EU/UN/UK sanctions, ownership opacity and a vetting grade
The AZ511 API is provided by AZ 511 (az511.com).
Yes. The AZ511 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 AZ511 API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the AZ511 API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The AZ511 API is served over HTTPS, so it's safe to use in production.