The Earth's curve is even slower.
The Earth moves approximately 1/24 of a degree around the sun in one hour. The angle that a plane crosses is far, far further.
Even with a "lateral force" of 10 mph, shouldn't your liquids spill out of your cups on a plane? They don't.
Here's a pic of the average plane routes.

Lets do the math.
The curve, is about a 30 degree angle.
This takes 5 hours to cross.
The speed of the plane, is 300 miles per hour.
We know, that a 90 degree turn, would require a 100 percent change in velocity.
We know, that a 180 degree turn, would require a 200 percent change in velocity.
So, we can guess that a 30 degree turn, would require a 33 percent change in velocity.
So, we divide 300 miles by 3.
100 miles.
Divide that by 5 hours.
20 miles.
You get 20 miles per hour, per hour.
The speed of gravity, is roughly 20 miles per hour, per hour.
Yet, the velocity required to keep Earth orbit, is 904 miles per hour.
The math, is undeniable. Flat earth, is true.
Gravity is a force, which depends on mass of bodies and distance between them. Acceleration due to gravity is denoted by 'g' . So gravity is a force and 'g' is acceleration.
no friction and velocity is accelerating / appearing to accelerate ??!! I have no idea what that implies! You should be clear on what you are trying to get at.
Let me explain gravity to you. It is not a magical accelerating force. It is simply a constant force.
Objects, will retain their momentum if they are not acted upon by friction. Gravity appears to "accelerate" objects, but what is really happening is simply that gravity is a steady force. Their velocity builds up, and appears to "accelerate" but it's just because it is not being acted on by outside forces and friction.