This question is very niched to aviation-themed-programming, but I hope I can possibly get some answers here.

I am creating a hobby project using Mapbox, Three.js and the ADSBexchange API. I am rendering aircrafts on a map (with Mapbox and Three.js) using their live position that I fetch every few seconds from ADSBexchange API. But when the altitude of an aircraft becomes 0, the data I am receiving is the exact same as the last API call (not even longitude and latitude change), plus the aircrafts that are on the ground, I am not retreiving data for at all. I have tried different endpoints of the API but none is giving me the positions of the aircrafts on the ground.

Could I just be using a wrong endpoint, or am I missing something really obvious? The one I am currently using is: Aircraft within 5 NM Radius