arrival/depatrure time differences from ASDI subscribers

I apologize if this is a very basic question.

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.


Thanks for the answer.

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.

Sounds like you’re writing a magazine or journal article?

Mark, maybe you should be careful to understand the context.

I am definitely not a journalist or book author: sorry if I gave the impression this was for the record! I am just an interested user of the FA, and as you can guess a non-aviation expert.

I noticed these time differences when I was looking at a couple of different sites, and since folks here are much more informed than me I figured you all could give me a simple explanation.

Didn’t sound like that to me.

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).

Yeh I see that now: my summary does seem a bit formal and stiff.

Anyway, I was just checking to see if my understanding was correct. Hopefully folks will let me know if I am in the right ballpark.


Great: thanks again all for the help.

There is also the issue that FlightAware has multiple data sources, so we don’t rely entirely on ASDI like most vendors.

That is really interesting: did not know there were other data sources.

Without giving away too much of the secret sauce, could you let me know a bit about what information is in these other sources?

And thanks again for the education on this.