I have noticed that the tracking data for many (most?) flights contains anomalous altitude and climb/descent data. For instance, a flight might have been descending from a cruise level of FL430 for a long time, then suddenly is shown as climbing again or even as level at a MUCH higher altitude. Can you explain why this happens so frequently? The feature would seem to be quite unreliable.
I am a new user, but am enjoying the site greatly. Too bad I can’t access it while I’m flying! 
We’ve also noticed this; it’s a bug in the data feed we receive.
Often a flight will be descending below 20000 ft and we’ll start receiving reports from another radar station that it’s at 30000 ft and holding level.
We’ve also seen stations in the northeast claim that a flight from Texas to Arizona is over New York.
We do correct some errors in the feed, but we’re still working on good ways to correct the two I just mentioned.
We’ve also seen stations in the northeast claim that a flight from Texas to Arizona is over New York.
Wow, that is scary! Kind of like when ATC asks me to “verify your destination is Kxxx” when it’s NOT!
Thanks for the prompt reply.
Those kind of questions are always really bizarre and make me wonder what’s going on behind the scenes.