Change drop down list depending on input content

I want to emulate this booking form.

If pickup is not an airport in the drop down list, it swaps to a google maps autocomplete drop down list.

I have a database and can show the two drop down lists independently. What I want to achieve is that as you type - depending on the input content - hide one list and show the other one. (That is how I think it's done according to the website code).

If anyone could shed some light I would be very grateful.

I asked web admin but doesn't know because it has been done for him 😥

source https://stackoverflow.com/questions/73505873/change-drop-down-list-depending-on-input-content