In What If?: Serious Scientific Answers To Absurd Hypothetical Questions, Randall Munroe, creator of the popular web comic xkcd, provides pages of in-depth responses to questions you probably never thought to ask.

Q. Which US state is actually flown over the most? — Jesse Ruderman

A. When people say "flyover states," they're usually referring to the big, square states out west that people stereotypically cross over while flying between New York, LA, and Chicago, but don't actually land in.

But what state do the largest number of planes actually fly over? There are a lot of flights up and down the East Coast; it would be easy to imagine that people fly over New York more often than Wyoming.

To figure out what the real flyover states are, I looked at over 10,000 air traffic routes, determining which states each flight passed over.

Surprisingly, the state with the most planes flying over it — without taking off or landing — is...

...Virginia.

This result surprised me. I grew up in Virginia, and I certainly never thought of it as a "flyover state."

It's surprising because Virginia has several major airports; two of the airports serving DC are actually located in Virginia (DCA/Reagan and IAD/Dulles). This means most flights to DC don't count toward flights over Virginia, since those flights land in Virginia.

Here's a map of US states colored by number of daily flyovers:

Close behind Virginia are Maryland, North Carolina, and Pennsylvania.

These states have substantially more daily flyovers than any other.

So why Virginia?

There are a number of factors, but one of the biggest is Hartsfield-Jackson Atlanta International Airport.

Atlanta's airport is the busiest in the world, with more passengers and flights than Tokyo, London, Beijing, Chicago, or Los Angeles. It's the main hub for Delta Air Lines — until recently the world's largest airline — which means passengers taking Delta flights will often connect through Atlanta.

Thanks to the large volume of flights from Atlanta to the northeast US, 20 percent of all Atlanta flights cross Virginia and 25 percent cross North Carolina, contributing substantially to the total for each state.

However, Atlanta isn't the biggest contributor to Virginia's totals. The airport with the most flights over Virginia was a surprise to me.

Toronto Pearson International Airport (YYZ) seems an unlikely source of Virginia-crossing flights, but Canada's largest airport contributes more flights over Virginia than New York's JFK and LaGuardia airports combined.

Part of the reason for Toronto's dominance is that it has many direct flights to the Caribbean and South America, which cross US airspace on the way to their destinations. In addition to Virginia, Toronto is also the chief source of flights over West Virginia, Pennsylvania, and New York.

This map shows, for each state, which airport is the source of the most flights over it:

Flyover states by ratio

Another possible definition of "flyover state" is the state that has the highest ratio of flights over it to flights to it. By this measure, the flyover states are, for the most part, simply the least dense states. The top ten include, predictably, Wyoming, Alaska, Montana, Idaho, and the Dakotas.

The state with the highest ratio of flights-over-to-flights-to, however, is a surprise: Delaware.

A little digging turned up the very straightforward reason: Delaware has no airports.

Now, that's not quite true. Delaware has a number of airfields, including Dover Air Base (DOV) and New Castle Airport (ILG). New Castle Airport is the only one that might qualify as a commercial airport, but after Skybus Airlines shut down in 2008, the airport had no airlines serving it.

Least flown-over state

The least flown-over state is Hawaii, which makes sense. It consists of tiny islands in the middle of the world's biggest ocean; you have to try pretty hard to hit it.



Of the 49 non-island states, the least flown-over state is California. This came as a surprise to me, since California is long and skinny, and it seems like a lot of flights over the Pacific would need to pass over it.

However, since jet-fuel-laden planes were used as weapons on 9/11, the FAA has tried to limit the number of unnecessarily fuel-heavy flights crossing the US, so most international travelers who might otherwise travel over California instead take a connecting flight from one of the airports there.

Fly-under states

Lastly, let's answer a slightly stranger question: What is the most flown-under state? That is, what state has the most flights on the opposite side of the Earth pass directly under its territory?

The answer turns out to be Hawaii.

The reason such a tiny state wins in this category is that most of the US is opposite the Indian Ocean, which has very few commercial flights over it. Hawaii, on the other hand, is opposite Botswana in Central Africa. Africa doesn't have a high volume of flights over it compared to most other continents, but it's enough to win Hawaii the top spot.

Poor Virginia

As someone who grew up there, it's hard for me to accept Virginia's status as the most flown-over state. If nothing else, when I'm back home with family, I'll try to remember — once in a while — to look up and wave.

(And if you find yourself on Arik Air Flight 104 from Johannesburg, South Africa to Lagos, Nigeria — daily service, departing at 9:35 a.m. — remember to look down and say "Aloha!")

Excerpt from WHAT IF? by Randall Munroe. Copyright 2014 by xkcd. Used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.