## Non-Stop, Long-Haul Flight Routes in the Southern Hemisphere

There are many non-stop, long-haul flight routes between different continents in the southern hemisphere, without crossing the northern hemisphere. These routes are only possible if Earth is a sphere, and impossible if Earth is flat.

Flat-Earthers claim that all long-haul flights south of the Equator always do a stop north of the Equator. In reality, there are plenty of non-stop routes between these locations, showing that Earth is a sphere.

## Airplanes Going Over Earth’s Curvature

To an observer on the ground, an airplane at 36000 ft will start going over Earth’s curvature at a distance of 400 km. However, we are also limited by atmospheric visibility. In an extremely best-case scenario, we can only see up to 240 km.

We can easily see ships going over Earth’s curvature, and flat-Earthers like to demand us the same thing for airplanes. In reality, at the typical distance a plane does that, it is far out of visibility range. But if it is very low, like when approaching a runway to land, it is possible to see the plane going over the curvature of the Earth.

## Curved Airplane Window and Observation of Earth’s Curvature

With careful planning, we can easily observe Earth’s curvature from an airliner. To “explain” the observation, flat-Earthers invented the excuse that it is caused by the distortion from the shape of the airplane’s window.

In reality, all camera lenses are curved, too, yet most of these lenses produce normal, rectilinear images. The fact that the shape of the window is curved does not mean looking through the window will produce a curved horizon.

Airline pilots are educated to understand that Earth is a sphere and depend on the knowledge to do their job. They have plenty of opportunities to observe Earth’s curvature, either visually or using the airplane’s instruments. They are also aware that there are people out there that somehow believe in flat Earth, and some of the pilots even actively debunk flat Earth in their spare time.

Flat-Earthers asked some of the pilots if Earth is flat and rudely recorded the conversation. Then, they would brag online if they can get the pilots to “admit” in camera that Earth is flat. In reality, these pilots are professionals on the job and aware of the erratic behavior of the flat-Earthers. They were just trying to get rid of these people as quickly as possible without making a scene.

## Airplanes Do Correct for the Coriolis Effect

Airplanes do correct for the Coriolis effect. They constantly make adjustments to counter forces that try to push them away from the planned route, including the Coriolis force.

Flat-Earthers claim the Coriolis effect does not appear to affect airplanes, and they use it to “prove” that Earth is stationary. In reality, the Coriolis effect does affect airplanes, and we do have to correct for it. But the effect is tiny, and we can safely ignore it in flight planning.

## Eötvös Effect: Direct Evidence Earth is a Rotating Sphere

Eötvös effect is the change in perceived gravitational acceleration when moving eastward vs. westward. An object will weigh slightly more when moving westward than when it is stationary or moving eastward.

The slight difference in weight due to the Eötvös effect can be measured in an experiment on a flight. The Eötvös effect is direct evidence that the Earth is a rotating sphere.

## Spirit Level on an Airplane

During cruising, an airplane is practically level. It is flying perpendicular to the direction of gravity. The aircraft is still flying following Earth’s curvature and continuously changes its orientation. However, not only its orientation changing but also the direction of gravity, having the same amount of change. As a result, a spirit level on a flight will not show us the difference in orientation of the airplane due to its motion following the curvature of the Earth.

## Human Perception of Speed and Acceleration

When aboard an airplane flying at cruising speed, we will not be able to feel that the plane is, in fact, moving at speed of more than 900 km/h. But if the plane changes its speed, turns or changes its altitude, we can easily feel it.

The same thing happens with the motion of the Earth. Due to Earth’s rotation, the surface of the Earth is moving at 1656 km/h near the equator. We never feel it because the speed is constant, or in other words, the acceleration is zero.

## Bottled Water: A Simple Device for Observing the Dip of the Horizon

On many flights, they would give away leveling devices to all passengers for free, so that everyone would be able to observe the dip of the horizon and proves Earth is a sphere. And as a nice side effect, to quench our thirsts, too!

Such devices are called ‘bottled water’. Using these simple ‘instruments’ on a flight, we can demonstrate that Earth is a sphere.

## The Taiwan–Los Angeles Flight (not from Bali) that was Diverted to Anchorage

There was a flight from Taiwan to Los Angeles that was diverted to Anchorage because one of the passengers gave birth to a baby. Flat-Earthers use the case as one of the first “evidence” from flight routes proving Earth is flat.

They are wrong. The case only tells us about the ignorance of these flat-Earthers about the distortion in a map projection. Their argument started with an elementary mistake of taking a straight line on a Mercator map between Taiwan and Los Angeles, and assume it as the “intended flight path.”

## The Failure of Flat-Earth Model to Explain Emergency Landings That Occur More to the South

The perpetrators of flat-Earth often take emergency landings as ‘proof’ of a flat Earth. They would point out that the diversion airports used for such emergency landings are somehow consistent with the flat-Earth map.

It is not a coincidence that all the cases of emergency landing they pointed out occurred far in the north. At the locations closer to the north pole, the distortion of the azimuthal-equidistant map (claimed by flat-Earthers as the ‘flat-Earth map’) diminishes. It would seemingly appear as if the ‘flat-Earth map’ can explain the choice of the diversion airports. In many other locations, though, the flat-Earth map would fail to explain it.