For example, if I were in Tangier, Morocco, and wanted to fly to Whangarei, New Zealand (the antipode on the globe) – wouldn’t it be about the same time to go up instead of across?
ETA: Thanks so much for the detailed explanations!
For those who are wondering why I picked Tangier/Whangarei, it was just a hypothetical! The-Minmus-Derp explained it perfectly: *Whangarei and Tangier airports are antipodes to the point that the runways OVERLAP in that way – if you stand on the right part if the Tangier runway, you are exactly opposite a part of the Whangarei runway, making it the farthest possible flight.*
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The is a safety reason, the are a lot fess airport where a plane could divert to in case of problems
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At all stages of flight planes must be less than X hours from an airport in case of emergencies. The number of hours depends on the plane.
When crossing the Pacific, there are airports just for this in Alaska and Hawaïi, and on the Atlantic side you have Iceland on the middle helping out.
Over the poles you have long streches without any airports, so this is avoided.
Because the poles are literally deserts. No airports. Engine fails, you land in water (or the actual desert that is Antarctica) and the closest ship will take half a day to come rescue you. That’s not the case when crossing the Pacific, Indian and Atlantic oceans.
Also wondering why you picked Tangier specifically lol
It’s called a [Polar Route](https://en.wikipedia.org/wiki/Polar_route) and they are somewhat common. If a route would be far shorter going over the artic, they do just that.
However, the risk of going over the artic is there are very few airports up there. So if a plane needs to make an unscheduled landing they have far fewer options. So if a flight path is similar, or a little longer, but it flies over more populated areas, the airlines will choose that route.
A few things that come to mind:
1) Practicality. In your example, you list Tangier and Whangare, as a city pair. This is an incredibly long and specific journey, with probably not that much of a market. If you were an airline, it wouldn’t make much sense to operate this flight, hoping enough people in Tangier would buy tickets on your airplane to Whangere. So what you do instead, is sell tickets from Tangier to some place like Singapore, and then have those passengers /connect/ on a different airplanes to various locations in the south pacific.
Even super long flights from big cities, Like New York (Newark) to Dehli, are mostly connecting passengers. Passengers fly from all over the U.S. and Canada to Newark, and then get on the big plane to Dehli. From there, maybe some stay in Dehli, but lots connect to other destinations in South East Asia.
2) Safety. Every airplane is certified to fly a certain distance “off shore” from a suitable landing field in case of emergency. Some aircraft are certified to fly further distances from land than others. In the early days of commercial jets, only four engine airplanes could fly extended distance off shore. As turbine engines became more reliable, it was eventually lowered to 3 and then 2 engine airplanes, as they got certified for such operations (ETOPS). https://en.m.wikipedia.org/wiki/ETOPS
Originally, the north atlanic routes follow the east coast of the US and Canada, then over Greenland, then Iceland, then finally over the UK, and into Europe. This routing was established decades ago. Interestingly enough, if you took a piece of string across a globe, and tried to make the straightest line you could between New York and Paris, while still maintaining.. say, /three hours of flight time on a single engine/ you would roughly get the same line as the north atlantic routes we have today.
3) The jet stream. There are two ways to cross the Atlantic and Pacific ocean.
North Atlantic Crossing routes (NAT Tracks) https://en.m.wikipedia.org/wiki/North_Atlantic_Tracks
And Pacific crossing routes (PACOTS) https://en.m.wikipedia.org/wiki/Pacific_Organized_Track_System
These routes are published evey 24 hours based on the ever moving jet stream. The design is to keep east bound flights in as much tail wind as possible, while keeping west bound flights in as little head wind is possible. This saves time, but most importantly, fuel.
4) Airspace. Geopolitical issues extend well above Earth into the sky into an undefined ceiling. For instance, if you were a US based airline, you would generally be prohibited from overflying Ukraine, Libya, North Korea, Syria, and Yemen, to name a few nations. During the cold war, Anchorage Alaska became a major cargo hub, which it still is today. This was partly because overflight of the Soviet Union was prohibited. Anchorage was the closest major airport to Asia, it could reach Japan, China, and South East Asia without overlying the USSR.
It depends, if you are in the northern hemisphere you may take ‘the great circle route’:
[https://en.wikipedia.org/wiki/Polar_route](https://en.wikipedia.org/wiki/Polar_route)
In theory, you could do a southern polar route, but no one seems to want to. The answers about needing to be x hours away from an airport are incorrect; a southern polar route would be in range of appropriate ETOPS 370 diversions provided the route doesn’t take you directly over the south pole. Antarctica is massive (it is 1.5 times the size of the continental US) so you could clip it and be legal.
ETOPS 370 stands for extended twin operating standard (or ‘engines turn or passengers swim’) 370 minutes. That is, the plane must be able to fly for 370 minutes on one engine. Turbines (the type of engine on almost every commercial aircraft) very rarely fail. ETOPS 370 is available on the Airbus A350. ETOPS 330 is available on the 777-ER. The Boeing 747 and the Airbus A380 and A340 do not need to comply with ETOPS. So, in theory, there are a few planes that could do a southern polar route.
But… we don’t? Look up the great circle route. Planes flying the shortest distance don’t usually fly “horizontally” because the earth is a sphere. On a map it looks like an arc that bends towards one of the poles. The earth is widest at the equator.
Actually we typically fly by the shortest distance which AI be a “great circle” whose diameter plane cuts through the center of the earth. It may go over one of the poles.
Flying a great circle, shortest route to reach another point on the surface of a globe, is done whenever possible. Saves on time and fuel.
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