Must be some way to do this from the DBCs considering they define the distances and flight related paths...
*Edit*
Good news, tested it flying between SW, Goldshire and Eastvale and the timers expected are about right, only that in-game there can be up to a second delay when you click and actually start to fly, e.g. or between path transitions (i.e. sw to goldshire then it has to hop you on from goldshire to eastvale, that transition can take enough time to add a couple of seconds to the total timer from start to finish if you fly and jump many different paths).
Going to make a function to iterate trough the various possible paths in-game, that exists of course, then store it in a file and check with the current InFlight.lua data and see how much off I am, hehe. If lucky and it's only some seconds differences then it may be my speed constant that needs changing, or changing depending on the path, there are some flags I am not sure what are on taxinodes so if lucky they hold the answer to the speed problem.
*Edit 2*
These are the times for single flights only (no connections):
http://pastebin.com/PJLHijdG (from, to, copper, time)
I've looked in the inflight data and must say it's scary how similar the times are, only a few weird entries like Sentinel Hill to Stormwind is 25 sec on inflight while around 80 on the calculations. :P
For chained flights one has to think about the start->node1 and nodeN->end times and skip them on paths in between, i.e. if you fly Stormwind -> Duskwood -> Blasted Lands one would have to skip the nodeN->end (landing) time between Stormwind and Duskwood, Duskwood and Blasted Lands you need to skip both launch and landing, and at the end you must skip the launch->node1 while include the nodeN->landing times to get it most accurate as you can.
In the DBC the taxi path names are localized so it's a bit tricky to make it easy to work on many locales, considering the ID in the DBC are not accessible trough game API (I think they should make it tough, hehe).
Anyway, these are my findings so far. I'll release my PHP script for the data management and such soon, it's not a big deal, and it's actually a bit noobish in layout.
Made it mainly to extract data from DBCs (actually their CSV files after using another program to convert the DBCs) to begin with.
About making the flightmaps tough, this shouldn't be too hard:
1. We have a list of all from and to paths, so all you have to do is scan this array of data and check "I am at X, when is from=X and store the to value in a table with a index of X" thus you end up with for example: {[2]={5,6,8}} where at node 2 you have access to nodes 5, 6 and 8. Then you can do a debt query and go further down, check where does 5 go to, where do 6 go to, e.g. When at the FP in-game you know where you start and you know where you want to go, and the game marks the path so you know the nodes in between, so with something smart you can recursively find these path names and by having some sort of library to convert the names into ID's for example, you can extract the times from the database above and sum up the different times.
I realize you loose the launch->node1 and nodeN->landing times but assume 1+-2 seconds differences in the mathematical from the actual version.
Besides, latency also plays a role, if you have 500ms you will notice slight alteration in the times anyway, you can't get the times 100% accurate, only estimates so it's not a bad idea to use the raw data to generate the flight times I think.
Sorry for blocks of text.
Is there any point me writing this btw? I got the impression someone else is benefiting from this information, maybe not, maybe it's just me...