[Diana]

Hi everyone, I recently saw some videos about whether the earth is round or flat, so I was thinking about the question of airplane flight and the shape of the earth and wanted to share some observations with you.

Have any pilots or passengers ever personally observed the nose of an airplane adjust during flight?

Does the horizon appear consistently flat at different flight levels and altitudes?

Has anyone tried photographing the horizon with a telescope or a high-powered camera to verify its curvature?

Is route planning based on a spherical Earth or a flat map more effective?

If the Earth is truly spherical, why don't instruments and navigation systems correct for curvature in real time?

[Gonzo]

As an air traffic controller of 27 years experience, I know that flight planning, routing and airspace design are all based on the round earth. In my experience, the myriad factors that come into play both in terms of exact route planned, and exact route subsequently flown, by aircraft often confuse flat earthers.

Aircraft in flight are constantly adjusting. They would do so regardless of the shape of the earth.

What leads you to believe that instruments and navigation systems are not 'correcting for curvature in real time'? What instruments?

[DuncanDoenitz]

Hi everyone, I recently saw some videos about whether the earth is round or flat, so I was thinking about the question of airplane flight and the shape of the earth and wanted to share some observations with you.

1.Have any pilots or passengers ever personally observed the nose of an airplane adjust during flight?

2.Does the horizon appear consistently flat at different flight levels and altitudes?

3Has anyone tried photographing the horizon with a telescope or a high-powered camera to verify its curvature?

4Is route planning based on a spherical Earth or a flat map more effective?

5If the Earth is truly spherical, why don't instruments and navigation systems correct for curvature in real time?

I am a retired aircraft engineer.  These are questions, not observations, but here goes;

1. As Gonzo said, an aircraft's attitude in flight is in a state of constant adjustment due to changes in course, altitude and the effects of the aircraft's inherent stability, auto-flight system (or pilot) reacting to turbulence.  On a round earth of the conventionally accepted form, circumference around 24,000 miles, an aircraft will theoretically have to pitch it's nose down by 1 degree in the course of 67 miles.  Do you think that the passengers and crew would notice this against the background of other movement? 

2. Yes.

3. What is the point?  by using magnification, the observer is focussing on a smaller arc of curvature than with the naked eye, so curvature would be less pronounced. 

4. Spherical.  Just look at a flight tracking site like FR24, and observe the south atlantic and south pacific.  There are now daily flights between Australia-South America, and Australasia-Chile.  These take place entirely in oceanic airspace; does this routing correspond with any of the various flat-earth maps you've seen?  Would the distance even be within the flyable range of any airliner on any flat earth map?  (At this point, I will point out that a flat-earth lurker will likely be on shortly, with his theory about "anomalous" winds and jetstreams boosting the groundspeed of long haul aircraft.  When he does, ask yourself how airline operations departments can plan to use winds of unknown direction and velocity?  How much fuel should the aircraft carry?  Jetstreams are an almost completely west-to-east phenomenon; how can they consistently give advantage to outward and return trips?).

5.  They do. 

[Diana]

As an air traffic controller of 27 years experience, I know that flight planning, routing and airspace design are all based on the round earth. In my experience, the myriad factors that come into play both in terms of exact route planned, and exact route subsequently flown, by aircraft often confuse flat earthers.

Aircraft in flight are constantly adjusting. They would do so regardless of the shape of the earth.

What leads you to believe that instruments and navigation systems are not 'correcting for curvature in real time'? What instruments?

I'm not claiming the instruments aren't calibrated, but I'm trying to understand, if the Earth is truly spherical, how do the flight instruments account for the curvature in their real-time calculations? For example, on long-distance flights, does the autopilot follow the curvature by continuously descending at a shallow angle, or does it rely entirely on the data from the waypoints?

[Diana]

1. I don't think anyone would notice your point
2. You say yes. Does that mean that pilots and passengers can indeed see slight changes in the horizon at different altitudes?
3. You mention that the curvature is less noticeable under a magnifying glass, which is interesting. But if you use a telephoto lens to photograph the distant horizon from a high altitude, is there any scientifically recognized experimental data that can quantify this curvature?
4. I understand your case of transoceanic flights in the Southern Hemisphere, which can only be explained by spherical routes. But are there any actual flight routes that appear to violate the shortest spherical route? If so, how can you explain it?

Hi everyone, I recently saw some videos about whether the earth is round or flat, so I was thinking about the question of airplane flight and the shape of the earth and wanted to share some observations with you.

1.Have any pilots or passengers ever personally observed the nose of an airplane adjust during flight?

2.Does the horizon appear consistently flat at different flight levels and altitudes?

3Has anyone tried photographing the horizon with a telescope or a high-powered camera to verify its curvature?

4Is route planning based on a spherical Earth or a flat map more effective?

5If the Earth is truly spherical, why don't instruments and navigation systems correct for curvature in real time?

I am a retired aircraft engineer.  These are questions, not observations, but here goes;

1. As Gonzo said, an aircraft's attitude in flight is in a state of constant adjustment due to changes in course, altitude and the effects of the aircraft's inherent stability, auto-flight system (or pilot) reacting to turbulence.  On a round earth of the conventionally accepted form, circumference around 24,000 miles, an aircraft will theoretically have to pitch it's nose down by 1 degree in the course of 67 miles.  Do you think that the passengers and crew would notice this against the background of other movement? 

2. Yes.

3. What is the point?  by using magnification, the observer is focussing on a smaller arc of curvature than with the naked eye, so curvature would be less pronounced. 

4. Spherical.  Just look at a flight tracking site like FR24, and observe the south atlantic and south pacific.  There are now daily flights between Australia-South America, and Australasia-Chile.  These take place entirely in oceanic airspace; does this routing correspond with any of the various flat-earth maps you've seen?  Would the distance even be within the flyable range of any airliner on any flat earth map?  (At this point, I will point out that a flat-earth lurker will likely be on shortly, with his theory about "anomalous" winds and jetstreams boosting the groundspeed of long haul aircraft.  When he does, ask yourself how airline operations departments can plan to use winds of unknown direction and velocity?  How much fuel should the aircraft carry?  Jetstreams are an almost completely west-to-east phenomenon; how can they consistently give advantage to outward and return trips?).

5.  They do. 

[Gonzo]

I'm not claiming the instruments aren't calibrated, but I'm trying to understand, if the Earth is truly spherical, how do the flight instruments account for the curvature in their real-time calculations? For example, on long-distance flights, does the autopilot follow the curvature by continuously descending at a shallow angle, or does it rely entirely on the data from the waypoints?

Because they have been designed to do so. What sort of flight instruments are you talking about? (there are many different kinds on instruments!) Do you mean what is often referred to as the 'artificial horizon'?

In most stages of flight, for most aircraft where fitted, the auotpilot will be in ALT SEL/VNAV modes, which will maintain whatever level is set in the autopilot control panel. Aircraft altimeters are basically barometers, so will be following a constant preessure plane, of, say, 1013.2Mb (29.92in). Dialling in 30,000ft might, depending on local air pressure at the surface/sea level, result in an aircraft flying at 29,000ft or 31,000ft. The key is that all aircraft in the same area of sky are using the same pressure datum to reference (which is why we tell all deaprting and arriving aircraft at my airport the local air pressure for them to enter into their altimeters). None of this is dependent upon the shape of the earth.

Any minute change in pitch due to the curvature of the earth's surface will be drowned out by the relatively massive changes felt by the passengers due to changes in air pressure and turbulent air masses.

There are lots of flight routes that don't follow the great circle route. This can be for many reasons -

- Airspace restrictions - many nations reserve large areas of airspace for military exercises and training, and there are lots of no-go airspace areas due to conflict.
- Route charges - Majority of nations charge the operators of aircraft flying through their airspace, in order to generate revenue to provide the ATC service. Some countries' charges are expensive, some not so much. An airline may try to avoid flying through expensive airspace, even if it lengthens the flight. It's a balance of airspace cost v fuel cost.
- Winds - a longer flight with a tailwind may use less fuel than a shorter flight with a head wind.
- Airspace route structure - the published airways and routes that aircraft file on their flight plan -  In busy areas, these will be designed to spearate directional flows of traffic, to ensure orderly and safe operations (just like one lane of a road goes in one direction, the other lane the other direction). This can often not be the shortest flight route for an individual aircraft, but it allows the airspace to handle far more aircraft at one time than if all the aircraft just flew their shortest route. 
Lots of other factors too.

[DuncanDoenitz]

1. I don't think anyone would notice your point
2. You say yes. Does that mean that pilots and passengers can indeed see slight changes in the horizon at different altitudes?
3. You mention that the curvature is less noticeable under a magnifying glass, which is interesting. But if you use a telephoto lens to photograph the distant horizon from a high altitude, is there any scientifically recognized experimental data that can quantify this curvature?
4. I understand your case of transoceanic flights in the Southern Hemisphere, which can only be explained by spherical routes. But are there any actual flight routes that appear to violate the shortest spherical route? If so, how can you explain it?

Thanks for coming back, Diana.  Welcome to the forumm btw. 

1.  OK.
2.  No, at atmospheric altitudes (ie, not in space) the horizon appears flat.  Imagine you're in a balloon at 50,000 feet. Look North, and let's say the horizon appears curved, that is, it's lower at the edges.  Now turn to your right and look East.  With a curved horizon, logic says tha the horizon will continue to curve down at the edges.  Keep turning right until you're bac looking North.  See my point?  It can't continue to curve downwards. 
3.  Don't know; not my speciallist subject.
4.  Kind of, but entirely logical.  The shortest distance between 2 point on a sphere is a Great Circle, but that is not necessarily the fastest, cheapest, safest route.  Amongst the considerations that disrupt a Great Circle are weather, wind velocity, diplomatic and political neccessity, cost of fuel etc.  For instance, commercial routes from Europe to the far east often route via the Gulf States; the fuel's cheaper.  And, of course, the need to remain within range of diversion airfields in case of emergency. 

And your question to Gonzo; aircraft maintain height primarily by reference to atmospheric pressure acting on the altimeter.  Pressure reduces with altitude above sea-level and it doesn't matter whether the Earth is flat, round or shaped like a Toblerone; autopilot monitors the altimeter and acts to keep the aircraft at a constant atmospheric pressure, ascending or descending as necessary.  Look at the isobars on a map, weather has a far greater effect on heightkeeping than earth-curvature. 

(edit, Gonzo answered this in greater detail whilst i was writing).

[Diana]

Thanks, I think I understand your explanation about autopilot, altimeters, and how flight routes are determined. It makes sense that small pitch changes due to earth’s curvature are negligible compared to turbulence and pressure differences, and that operational factors like airspace and winds play a bigger role in flight paths
I’ve seen some people claim that certain flight routes or autopilot behavior prove the Earth is flat. Given what you explained, it seems that most of these observations could be explained by air traffic rules, pressure settings, and operational choices. From your experience, is there anything in actual flight that could realist

I'm not claiming the instruments aren't calibrated, but I'm trying to understand, if the Earth is truly spherical, how do the flight instruments account for the curvature in their real-time calculations? For example, on long-distance flights, does the autopilot follow the curvature by continuously descending at a shallow angle, or does it rely entirely on the data from the waypoints?

Because they have been designed to do so. What sort of flight instruments are you talking about? (there are many different kinds on instruments!) Do you mean what is often referred to as the 'artificial horizon'?

In most stages of flight, for most aircraft where fitted, the auotpilot will be in ALT SEL/VNAV modes, which will maintain whatever level is set in the autopilot control panel. Aircraft altimeters are basically barometers, so will be following a constant preessure plane, of, say, 1013.2Mb (29.92in). Dialling in 30,000ft might, depending on local air pressure at the surface/sea level, result in an aircraft flying at 29,000ft or 31,000ft. The key is that all aircraft in the same area of sky are using the same pressure datum to reference (which is why we tell all deaprting and arriving aircraft at my airport the local air pressure for them to enter into their altimeters). None of this is dependent upon the shape of the earth.

Any minute change in pitch due to the curvature of the earth's surface will be drowned out by the relatively massive changes felt by the passengers due to changes in air pressure and turbulent air masses.

There are lots of flight routes that don't follow the great circle route. This can be for many reasons -

- Airspace restrictions - many nations reserve large areas of airspace for military exercises and training, and there are lots of no-go airspace areas due to conflict.
- Route charges - Majority of nations charge the operators of aircraft flying through their airspace, in order to generate revenue to provide the ATC service. Some countries' charges are expensive, some not so much. An airline may try to avoid flying through expensive airspace, even if it lengthens the flight. It's a balance of airspace cost v fuel cost.
- Winds - a longer flight with a tailwind may use less fuel than a shorter flight with a head wind.
- Airspace route structure - the published airways and routes that aircraft file on their flight plan -  In busy areas, these will be designed to spearate directional flows of traffic, to ensure orderly and safe operations (just like one lane of a road goes in one direction, the other lane the other direction). This can often not be the shortest flight route for an individual aircraft, but it allows the airspace to handle far more aircraft at one time than if all the aircraft just flew their shortest route. 
Lots of other factors too.

ically be used to ‘see’ the curvature of the Earth?

[Diana]

Thank you for your detailed explanation! I understand the arguments regarding altimeters, autopilots, and why the horizon appears flat at normal flight altitudes. It's also reasonable to assume that operational factors like route planning, fuel costs, and weather have a greater impact on flight paths than the curvature of the Earth. These aren't actually my areas of expertise, I'm simply responding based on my own understanding and some research
Some people argue that if the Earth were truly curved, pilots should see noticeable curvature during long flights, or autopilot would need constant adjustments for it. In your experience, have you ever noticed anything during flights that could be interpreted as visible evidence of the Earth’s curvature—or lack thereof?

1. I don't think anyone would notice your point
2. You say yes. Does that mean that pilots and passengers can indeed see slight changes in the horizon at different altitudes?
3. You mention that the curvature is less noticeable under a magnifying glass, which is interesting. But if you use a telephoto lens to photograph the distant horizon from a high altitude, is there any scientifically recognized experimental data that can quantify this curvature?
4. I understand your case of transoceanic flights in the Southern Hemisphere, which can only be explained by spherical routes. But are there any actual flight routes that appear to violate the shortest spherical route? If so, how can you explain it?

Thanks for coming back, Diana.  Welcome to the forumm btw. 

1.  OK.
2.  No, at atmospheric altitudes (ie, not in space) the horizon appears flat.  Imagine you're in a balloon at 50,000 feet. Look North, and let's say the horizon appears curved, that is, it's lower at the edges.  Now turn to your right and look East.  With a curved horizon, logic says tha the horizon will continue to curve down at the edges.  Keep turning right until you're bac looking North.  See my point?  It can't continue to curve downwards. 
3.  Don't know; not my speciallist subject.
4.  Kind of, but entirely logical.  The shortest distance between 2 point on a sphere is a Great Circle, but that is not necessarily the fastest, cheapest, safest route.  Amongst the considerations that disrupt a Great Circle are weather, wind velocity, diplomatic and political neccessity, cost of fuel etc.  For instance, commercial routes from Europe to the far east often route via the Gulf States; the fuel's cheaper.  And, of course, the need to remain within range of diversion airfields in case of emergency. 

And your question to Gonzo; aircraft maintain height primarily by reference to atmospheric pressure acting on the altimeter.  Pressure reduces with altitude above sea-level and it doesn't matter whether the Earth is flat, round or shaped like a Toblerone; autopilot monitors the altimeter and acts to keep the aircraft at a constant atmospheric pressure, ascending or descending as necessary.  Look at the isobars on a map, weather has a far greater effect on heightkeeping than earth-curvature. 

(edit, Gonzo answered this in greater detail whilst i was writing).

[DuncanDoenitz]

No; but that is what I would expect.  It's curved, but the sheer enormity of it makes the curvature imperceptible. 

[Diana]

You can't see a noticeable curvature from an airplane simply because the Earth is so big
Photos taken by high-altitude balloons and astronauts can clearly show the curvature of the Earth, so the Earth may really be round, which may be the scientific answer.

No; but that is what I would expect.  It's curved, but the sheer enormity of it makes the curvature imperceptible.