When I compare some flights between FlightAware and other ASDI feed subscribers, I will sometimes see a difference in arrival or departure times for a particular flight. Typically this will be a couple of minutes but it can be as many as a couple of hours. Since everyone is getting the same feed, I would think these times would match identically.
I assume that the providers are using something besides the messages or perhaps there are other definitions of departure/arrival besides wheels up/down.
Can someone provide a pointer here to help me understand the differences?
There’s an art and a science to interpreting the ASDI feed. What messages correspond to which flight, what messages are erroneous, etc. Some other sites also have gate data, and may display that instead of wheels up/down.
If you could, let me know if this a good summary:
Occasionally there will be flights where there is something unusual with the ASDI data, say the landing message was sent but the plane is still listed as traveling at a decent speed. In such cases FlightAware make a best guess as to what is going on and approximates the landing time based on some algorithm. Other vendors may do the same, but because of algorithm differences they will have different landing times.
It’s just the way you said it. I often do that too – restate something back, to check whether I understood it. But your specific phraseology reminded me of a journalist trying out a paragraph for an article (or, if you’re a professor, a scholarly journal).