www.ourairports.com provides free data for 55,556 airports/heliports/etc worldwide. The data is made available via .CSV dumps that are frequently updated. However, the workflow of downloading these files and transforming them into modern-day data formats (like JSON) and making use of that in applications is time consuming and sometimes error-prone. The OurAirportsApi.com is a set of endpoints that let you query exactly the same data, in a fast, reliable and intuitive way. I use the same data in multiple applications and depend on this API system to keep them all running (so I am personally invested in keeping it running & performant).
The data files are automatically updated every 30 days.
Please see the documentation at https://www.ourairportapi.com/StaticHtml/default.html for details.