Only a moment's consideration will reveal the amazing possibilities for our aviation community.Sam (KJ4CKK) has installed a Byonics MicroTrak-300 in his self-built RV6 kit aircraft (which took him 995.25 hours to build) and prepared a very nice guide for non-ham aviators about getting a license and installing an APRS tracker in a plane. Tracking airplanes is becoming more and more popular.
His plane's tactical callsign (as assigned by the FAA) is N399SB. Currently the last received position seems to have a lat/lng of (nearly but not exactly) 0/0 , probably a bad GPS fix, but just pick another day from the date menu on the right to see some of his flight tracks. They look even better on Google Earth.
Some more planes: N789PH (RV-9A) OH-XKR (Kitfox 4) OH-XST (experimental) N821RP (Long-EZ)
vansairforce.com has a discussion forum dedicated to APRS tracking of airplanes.