And the amount they would need to curve would be hidden in the noise.
They would not be able to tell, not without incredibly precise equipment.
Again, when planes are flying, they maintain their altitude.
The pilot or autopilot will constantly be adjusting the plane to do so.
As they do that, there is no need for them to specifically account for the curvature.
Because there IS no 'curvature' to ever ACCOUNT for!
For example, a 757 flies at about 500 mph (or 850 km/h) cruising speed, which is 8.33 miles per minute.
1 mile of 'curvature' is about 8 inches. So a 757 would fly over 8.33 x 8" 'curvature' per minute, every minute of flight, which is 66.64" of 'curvature' per minute, or 5.55 feet 'curvature' each minute.
Planes MEASURE level flight, with instruments like the VSI, or Vertical Speed Indicator, linked to the Altimeter. When a plane ascends from ground, the VSI measures it in FPM, or Feet Per Minute in ascent, while the altimeter measures all of it in feet above ground, where it started from. If the plane was at sea level, for example, the altimeter reads 0 feet altitude. If the plane was 200 feet above sea level, the altimeter reads 200 feet altitude, even if it's still on the ground itself.
When the plane ascends to, say, 35,000 feet within, say, 15 minutes time, the VSI measures the ascent in Feet Per Minute, throughout the ascent to 35,000 feet within a 15 minute period.
Of course, the ascent varies over that period, ascends slower at take off than afterwards, with more speed, with less air resistance when higher up, and is measured throughout, by their instruments.
Any ascent or descent will be measured by the VSI in FPM, which is also measured by the altimeter, in feet above ground, or sea level, which is 0 feet altitude.
You believe planes simply 'adjust' to a 'curvature', no need to even MEASURE for it, or ever ACCOUNT for it!
No, planes don't HAVE to account for 'curvature', and they don't HAVE to measure for 'curvature', since there ISN'T any 'curvature' TO account for, TO measure for!
The VSI measures ANY ascent or descent within air, by any variance in air pressure, when at LEVEL flight in air. Which really means, in EQUAL, in OPTIMUM air pressure.
There's only ONE way to fly in air, at equal air pressure, or in optimal flight, which is level to the air above Earth, same as level ON the Earth, because Earth is flat, and level, and air flows above the Earth in flat, horizontal paths, which is why level flight, is the optimal path to FLY in air.
If there WAS any actual 'curvature' of the Earth's whole surface, of about 8 inches per one mile distance, and squared per additional mile, it's certainly something we can measure, if it exists. But we cannot measure anything of it, because it does NOT exist.
So if a 757 flew over 'curvature', it would have to fly a CURVED path, it's the only path it COULD fly in, to match the CURVED surface below it.
That's simple to understand, a plane must fly a curved path, over a curved surface, but a level, flat path, over a level, flat surface.
To claim planes fly over a curved surface, at altitude, you must fly in curved paths.
And we'd have to measure these curved paths, same as any OTHER path would be measured.
The descent of our 757, at 500 mph, if it WERE a curved surface, would be something like 5-6 feet per minute of a CONSTANT descent, to match up with a curved surface, and it's absurd to claim this happens by itself, in all planes, just because you say so!
If planes DID fly over a curved surface, in a curved path above it, they'd measure it as a descent, and in several feet per minute, which means, there's no descent, no curved paths flown at all.
When you refuse to accept our measurements, with our instruments, that show, again and again, the Earth is flat, and measures as flat, every way possible TO measure it, without fakery involved, you'll believe it, anyway.
Any argument which hopes to change the very DEFINITION of a word, or term, is doomed to fail. Or already HAS failed.
To measure descent, or ascent, is very important to know, and it's very well known, today.
Nobody has ever said, 'Level doesn't measure level as flat and straight across, but it's used that way, and works perfectly that way, it's really level to the Earth's 'curvature', if it could ever be MEASURED anywhere at all. Just because nobody can prove it exists, by any sort of measurement, doesn't mean it's all just made up crap, or anything!
I'd like you to explain how our VSI measures a descent, or an ascent, in feet per minute, all the time, every time, day after day, doesn't prove it WILL measure ANY descent or ascent, within our flights...
A 757