Why long-haul flights curve over the North Pole

HostIf you have ever been on a long flight, maybe to London or Tokyo, you have probably spent some time staring at that little map on the screen in front of you. You're trying to get across the ocean, but the line showing where the plane is going looks like a giant, weird arch that heads way up toward the Arctic. It looks like a massive detour. Why do we take such a curvy path instead of just flying in a straight line across the water?

GuestIt does look like you're going way out of your way, but the truth is that the straight line you see on your screen is the lie. The problem starts with the maps we have been using since grade school. Most of those maps are flat, but our world is a ball. When you try to flatten a round ball onto a square piece of paper, everything gets stretched out. The stuff near the top and the bottom gets pulled wide. So, when you draw a line on that flat map, it looks straight to your eyes, but if you were to look at that same line on a globe, it would actually be a long, wasteful curve.

HostSo, when I'm looking at my seatback screen and I see that big arch going up toward the North Pole, I'm actually seeing the shortest path possible?

GuestExactly. You can test this at home with a piece of string and a globe. If you pull the string tight between New York and Hong Kong, it won't stay down near the middle of the globe. It naturally slides up toward the top, over the Arctic. That's the true straight line. Pilots call these great circles. Because the earth is fattest at the middle and gets skinnier as you go up toward the poles, cutting across the top is like cutting the corner on a racetrack. It saves hundreds of miles and a lot of time.

HostOkay, but if the map is that wrong, why do we even use it? It feels like it just confuses everyone.

GuestWe use it because it's really good for one specific thing, which is keeping directions clear. If you want to sail a ship north, a flat map makes it easy to see that path. But it fails at showing size and distance. On a standard map, Greenland looks as big as Africa, but in real life, Africa is fourteen times larger. Since the map stretches the top of the world so much, the shortcut over the pole looks like a huge, unnecessary loop, even though it's the quickest way home.

HostThat makes sense for the distance, but the air up there must be a nightmare. I mean, it's the North Pole. Is it actually safe to fly a giant jet over all that ice and emptiness?

GuestIt's safe, but it takes a lot of planning. For a long time, we actually didn't fly over the pole much. Part of that was because of the cold. When you're up that high, the air is already freezing, but over the Arctic, it can get so cold that the jet fuel starts to turn into a thick slush. The fuel doesn't just freeze like water, it gets gooey, which is a big problem for the engines. Modern planes have systems to keep the fuel moving and warm, but pilots still have to keep a very close eye on the temperature. If it gets too low, they might have to fly faster or drop to a lower altitude where the air is a bit warmer.

HostBut what happens if an engine fails? There are no runways in the middle of the Arctic Ocean. That seems like a huge risk just to save some gas.

GuestThat was the main reason we avoided it for decades. There's a set of rules for how far a plane can be from an airport at any time. It used to be that if you only had two engines, you had to stay within sixty minutes of a place where you could land. There just aren't enough runways in the deep Arctic to make that work. But engines have become so reliable now that many planes are allowed to be five or six hours away from an airport. Still, even today, if a plane flies over the pole, the airline has to make sure there are specialized tracks and gear at remote snowy airfields, just in case they have to put the plane down in the middle of nowhere.

HostSo it's a mix of geometry and trust in the engines. But I have also heard that the wind plays a part. Sometimes I see planes take a path that looks even longer than the curve you're talking about.

GuestYeah, the wind is the one thing that can beat geometry. There are these huge rivers of fast-moving air high up in the sky called jet streams. They can blow at two hundred miles an hour. If you're flying with the wind at your back, it's like being on a fast moving walkway at the airport. You might fly a few hundred extra miles just to stay in that wind because the speed boost saves you more time and fuel than taking the shorter, straight path.

HostSo a pilot might look at the map and decide that the shortcut over the pole is actually slower because they would be fighting a headwind the whole way?

GuestRight. Every single flight is a new math problem. They have to balance the shape of the world, the heat of the fuel, and the speed of the wind. Sometimes the curve over the pole wins, and sometimes they stay further south to catch a ride on a wind current. It's never just about drawing a line from point A to point B.

HostThe pilots have to carry cold weather gear too, right? I read somewhere that they have to have polar suits in the cockpit.

GuestThey do. If a plane has to land on the ice, the crew and the passengers need to be able to survive until help arrives. They carry heavy parkas, boots, and even special tents. They also have to think about how to talk to the ground. Up at the very top of the world, normal satellites don't always work well, and the magnetic poles can mess with the tools used to find the way. It's a harsh place to do business, but the pull of saving fifty thousand pounds of fuel on a single trip is usually enough to make the trip worth it.

HostThat glowing line on the screen is basically a plane finding a shortcut on a world that refuses to stay flat.

GuestThose paths are the only way to make a round world fit into the schedules of people who just want to get across it as fast as possible.

HostThe little plane icon on the seatback map is just doing the math that our eyes can't see.