This is probably the most frequently asked question! The data is from here: http://ourairports.com/data/

I had to limit the number of airports displayed for performance reasons. I filtered the airport data so that only those airports with scheduled services and which are denoted "large" or "medium" are included (according to OurAirports), bringing the number down to 2,980.

Suppose that'll explain why there are at least three airports included in Ireland that have no scheduled services at all: the data's from nearly a decade ago

I am amused how airports like Lands End (which was grass runways only before 2014), and Chester(!!) made the cut. Plymouth closed in 2011

However that's all nitpicking, this is a pretty cool map, I'd never encountered Voronoi diagrams before.

Interesting. The data is from 2014, which is when I created the visualisation. Perhaps I should auto-update it every so often!

Most recent item on "recent changes" was five years old in 2014. Galway Airport's certainly been shut for a lot longer than that.

St Helena airport is open and technically operational. It's certainly one of the most remote airports on the planet (this happened post 2015)

It would be nice if there was a slider for N. I like to think my computer is recent, but evidently it is not!

I noticed they included most all the tiny regional airports in Iceland, but left out ones like Kulusuk in Greenland, which receives international air traffic.

Receiving international traffic is actually not a good measure of an airport's significance. Grand View International (WN23), for example, receives international traffic (from Canada), but has only a single 1700-foot grass runway. (It's also private.)

LHPR does a lot of business for Audi, 33 000 passengers a year between the Hungarian factory and the Ingolstadt parent plant in Germany and also some cargo as well. There are charters as well. So it receives international air traffic, alright but there are no scheduled flights simply because the area airports have no capacity problems. With three capitals -- Vienna, Budapest and Bratislava -- all within an hours drive in an imaginary scenario where those would be congested it would be booming but this is not London.

That is weird indeed. Especially since there are regular scheduled flights from the Reykjavík airport[1] to Kulusuk. Reykjavík airport is included, along with most airports that have scheduled flights from there (like Ísafjörður and Egilsstaðir) but not Kulusuk.

[1]: not to be confused with the larger Keflavík international airport that handles almost all international flights to Iceland

Agreed - this leads to many of these subset areas being displayed as much larger than they should be, while others should be larger. Either eliminate class D, or don't - to be inconsistent seems pretty pointless.

You will find the pattern, such as it is, explained at http://ourairports.com/about.html#credits .

Mammoth is also missing, which has commercial flights, as does Bakersfield (also missing).