We need an API connection to a free airport codes database, such as https://www.air-port-codes.com/.
The integration should be done in a form created with “Gravity Forms”.
The following website Full charter flight - Book now with PASflights! serves as a template for the functionality. If, for example, Paris is entered in the “From” field, suitable airports are automatically displayed and can be selected. Fluid search must also be a component. So, that matching is already started as soon as I enter the first letter.