This is a section of the aprs.fi user guide.
In addition to the real-time map on top of the Google Maps, aprs.fi also exports the real-time APRS view in the KML format so that it can be viewed in Google Earth. Google Earth provides a very nice 3-dimensional view which is especially useful for viewing flying objects such as planes and balloons. From the GE site:
Google Earth lets you fly anywhere on Earth to view satellite imagery, maps, terrain, 3D buildings, from galaxies in outer space to the canyons of the ocean. You can explore rich geographical content, save your toured places, and share with others.
Once you have installed Google Earth, you can click on the Google Earth KML link on the right side of the real-time map.
If you are tracking one or more stations, Google Earth will open up tracking those stations. Once Google Earth has started up:
If you're not tracking a specific station, simply zoom in at the area of interest. The KML view will display at most 1000 stations at a time, and a warning will be displayed when the limit is met. Zoom in to reduce the amount of stations in view.
aprs.fi user guide