An explanation for that may be that airplanes (unlike cars and trains) keep their turning forces almost perfectly downwards. A turn in a car or train has a side

An explanation for that may be that airplanes (unlike cars and trains) keep their turning forces almost perfectly downwards. A turn in a car or train has a sideways component, but a plane banks in the turn so the force is still pointing straight down at the floor. Take a look at your coffee next time you're on a flight, it remains level in turns while in a car it will move to one side. Unfortunately planes have a "less than 1g" feeling in turbulence that many people also get sick from. Just in a different way.