Pretty much what the topic asks.

Anyone have an idea of how fast a healthy dragon can fly? (if it matters: most of this will be at fairly high altitude, and it would be more of a long distance travel flight than a sprint, I think). I really have no idea how much their flight is based on physics (where larger birds may give a ballpark sort of number) and how much is based on magic (where I have no idea).

I'd have them travel at exactly the speed of plot, especially when you consider the ways they could modify their flight (spirits with appropriate powers, etc).

Eastern dragons and feathered serpents have 30/100, while western dragons travel at 30/60, according to the SR4A.
So, at around 36 km/h when moving normally, and between 72 (western) and 120 km/h when "running". Sprinting would be faster still.

No idea if there are values given in SR5.

Of course, what Critias said. Magic makes everything faster.

Note: not much of spoilers below, since this is entirely NOT per the plot of Boston: Lockdown. But just to be safe ... just mouse over to read it.

The runners are being carried out of the Boston quarantine zone clutched in dragon talons (instead of selling all their info for corp millions, they traded it to the dragon to be taken out when he made his break). They don’t have the right sort of breathing apparatus for altitudes, and he’ll be going up to Mt. Everest like heights (as well as wrapping himself in all the concealment he can manage with his draco-magic boosted by a powerful dragon ley-line). I figure after an hour or so of cruising he’ll notice that the runners aren’t wiggling much anymore, and he’ll care just enough to go dump them off somewhere isolated and make sure they are alive (and anyway his talons will be getting tired).

Exactly where doesn’t really matter, from a plot point of view. I’m probably going to drop them right in the middle of an adapted Redneck run (from Koekpan’s thread of that name). But for verisimilitude and colour, I figured I’d open up google earth view, look at the right general distance from Boston, and pick a spot. Barring any actual data it will probably be in the Adirondacks, or possibly the former coal country in Pennsylvania. Although they never did talk about direction, it could equally be in New Brunswick or Quebec or somewhere else entirely not in the direction of Seattle.

Bannockburn: I skipped from 2nd to 5th: is that ground/air, metres per 3 second turn? (just not sure the format for movement in 4th)

And yes, I guess one question is how big of a spirit it uses.

That's walking/running for flight speed in metres per 3 second turn, for adult dragons.