Have you ever been on a long-haul flight and wondered why your aircraft is taking a curved route instead of flying in a straight line when you look at the inflight map?
This is particularly noticeable when flying between Europe and the U.S. when aircraft will fly over Greenland and Northern Canada rather than just simply flying from point A to B as it would visually appear on a map.
The reason for this is down to simple mathematics and physics. The circumference of the Earth is a lot further around the equator than it is at higher or lower latitudes towards the poles of the earth, such is the spherical shape of our planet.
Flying around the smaller circumference of the Earth is called the “Great Circle Route” and also very noticeable for flights from the U.S. to Asia that will fly far above Alaska and Siberia rather than what would appear to be a straight line.
If you think about drawing a line around a globe in the middle where it is widest, versus towards the North or South poles, the differentiation of distance begins to become apparent, and it not only saves a huge amount of time but also fuel.
Because the Earth revolves on its axis, this forces the equator to “bulge out” and be wider. Despite what some theories suggest, the Earth is not flat, and so curvature becomes an incredibly important factor in routes aircraft take. Similar to the Earth itself, aircraft, therefore, take flight routes that also appear to be a curved line, tracing the Earth’s shape.
Flight paths are mapped out before aircraft take off, depending on the shortest and most efficient route, and flight paths can even change during flight depending on weather, wind and jetstreams, to name just a few variable factors.
As well as the curvature of the Earth, jetstreams are another important factor in why aircraft may not take what appears to be a completely direct route. Jetstreams can sometimes have tailwinds above 200 miles per hour, and that is going to get an aircraft to where it needs to be much quicker, whilst burning a lot less fuel. Contrastingly, if an aircraft would be flying head-on into a 200 mile per hour wind, flight planning may try alternative routes to avoid this.