Why Planes Avoid Flying over the Pacific Ocean

You'd think this is a safety issue at first. After all, the Pacific is the largest and deepest ocean on Earth—if a plane got in trouble over such a vast expanse of water, how's a pilot supposed to find a safe place to land? Alaska's not exactly crawling with international airports, but it sure beats being stranded in a watery nowhere. That seems like a pretty iffy tourism slogan, though: "Alaska: At least it's not sinking!" Sorry, Alaska.

Thinking it's a safety precaution wouldn't be wholly wrong. Pilots, of course, love routes with more available airports just for emergencies, though this is highly unlikely. Of course, losing an engine 30,000 feet above the Pacific is unnerving. But safety is not the central reason airlines do not use straight east-west routes over the ocean. It all just has to do with fuel and time-saving.

An airline makes money to the extent that it can move people quickly and inexpensively. People, in turn, would generally prefer to be moved as soon as possible, so it's a win-win situation for the airlines and its passengers. And the paramount consideration in how one flies is time. Except in special situations like the presence of jet streams or the vagaries of the weather, the quickest way is pretty much always the closest to a straight line.

But if you look at the path on a flat map, that is not a straight line! This is confusing because we're used to seeing the world on a two-dimensional plane. Because Earth is a sphere, a straight line looks different in three-dimensional space.

Let's perform an experiment. If you have a globe, stretch a string between Los Angeles and Tokyo. When you pull it tight, you'll see that the string has started to curve up, following Earth's curve. This effect is actually enhanced because our planet isn't a sphere; it is slightly wider at the equator.

The Earth's rotation causes the midsection of the Earth to bulge out, much as spinning on a merry-go-round pushes you outward.

If you wrapped a string around the Earth at the equator, you'd be 24,900 miles around the planet. If you did the same thing through the poles, you'd need 24,860 miles of string. This 40-mile difference might seem small, but it significantly affects the planet's surface area. That slight difference in the number means that an airplane flight that appears to be a straight line is often longer if a plane heads straight north or south, for instance, to try and go perpendicular to the line they think they are flying on.

Airplanes do cross the Pacific Ocean, especially when headed to Australia. Airplanes do venture over open water to circumvent storms. While some of this severe weather can be outclimbed by the aircraft, thunderstorms have been known to reach over 60,000 feet, which would make it very difficult to do. Severe turbulence can result in injuries to passengers and crew, hence the importance of keeping your seatbelt secured at all times. Air, too, will provide a smoother ride over the oceans, as there will be less turbulence from land masses. This is because water distributes heat better than soil, resulting in fewer hot air currents.

Another big thing to consider about flight paths is air currents, the most especially about jet streams. These high-altitude currents, at the top of the troposphere, can often reach speeds of over 200 mph.

There are four important jet streams, two running in each hemisphere, mainly from west to east. The polar jet stream runs close to the Arctic Circle, and the subtropical jet stream runs near the equator, which supports air travel. Aircraft flying with the help of a jet stream will have their travel time reduced. Aircraft flying against it will take much longer to reach their destination. However, jet streams are not all good, as they also cause clear-air turbulence at the edges, which becomes nearly unpredictable. Such turbulent air currents have much higher force compared to clear-air turbulence and put even a more significant stress on flight planning—to correctly position the aircraft within jet streams and, if possible, avoid some of the risky clear-air turbulence areas. Understanding how these flight routes work often factors in elements that we do not even think about as a part of our daily lives. The jet stream affects stuff tens of thousands of feet into the air. And the curvature of the Earth matters only when traveling at high rates of speed over huge distances.