Why Flights to Asia Often Detour Over Alaska: The Science Behind Flight Paths

Introduction

The author jokes about needing a vacation in Korea or Japan, then notices that a flight to Asia is routed over Alaska. This sparks a deep dive into why airlines choose seemingly indirect routes.

Safety First

• Pilots prefer routes with more alternate airports in case of emergencies.
• Over the vast Pacific, an engine failure would leave few safe landing options.
• While safety is a factor, it isn’t the primary driver of the Alaska detour.

Fuel Efficiency and the Fastest Path

• Airlines are businesses; they aim to move passengers quickly and cheaply.
• The fastest route is usually the one that minimizes distance, which on a sphere is a great‑circle route, not a straight line on a flat map.
• On a 2‑D map the path looks like a big curve, but on a globe it is the shortest distance.

The Earth’s Shape Matters

• Earth is an oblate spheroid: about 40 mi wider at the equator than pole‑to‑pole (24,900 mi vs. 24,860 mi).
• This bulge, caused by the planet’s rotation, means that a route that arcs toward higher latitudes can be shorter than a “straight” equatorial line.
• The author demonstrates this with a string on a globe, showing the great‑circle line between Los Angeles and Tokyo bends northward.

Weather, Turbulence, and Comfort

• Storm avoidance: Aircraft steer around hurricanes, tropical storms, and even tall thunderstorms that can reach 60,000 ft.
• Smoother ride over water: Oceanic air is more uniform; less hot‑air‑rising turbulence than over land.
• Jet streams: High‑altitude wind bands (polar and subtropical) flow west‑to‑east at 80‑200 mph.
• Riding a jet stream can shave hours off a flight.
• Flying against it can add time and fuel.
• Edge of a jet stream can produce clear‑air turbulence, which is hard to predict and can be severe (e.g., 1997 Tokyo‑Honolulu incident).

Practical Takeaways for Passengers

• Keep seat belts fastened at all times; turbulence can occur unexpectedly.
• The route you see on a flat map is not the actual distance the plane travels.
• Detours over Alaska are often a result of great‑circle routing combined with safety and fuel considerations, not a mistake.

Closing Thoughts

Understanding flight paths involves geometry, physics, and economics—factors most travelers never consider while watching the clouds drift by.

Airlines route flights over places like Alaska because the great‑circle route, safety considerations, fuel savings, and atmospheric conditions make it the most efficient and reliable path, even if it looks odd on a flat map.