I am questioning the power of gravity to keep a plane from flying straight without having to follow the curvature of the earth and you all respond with I don't understand physics.
Level means not curved.
In 10 miles the earth drops 66 feet.
In 20 miles the earth drops 266 feet.
In 30 miles the earth drops 600 feet.
A fighter jet can go 1 mile in 10 seconds.
In 5 minutes the curved earth would be 600 feet, plus the altitude before leveling off, below a jet flying straight.
--Dave
Level DOES NOT mean "not curved"!
It means perpendicular to the pull of gravity. Every level you've ever used works on that single principle.
If there is a related term that you could be accurately used to mean "not curved" it would be the word "true". Although that may not always be the case depending on the context. To say something is "true", in this sense, simply means that it is consistent with itself and/or something else. So, for example, if you're laying tile on a back-splash, you would want your grout lines to be both level AND true. The trueness of the grout lines means that they are laid in a consistent manner all the way across the back splash as well as being consistent with the counter top.
Aside from "true" the only other word I can think of to convey "not curved" in the way you are meaning it is "straight". But in no case does "level" mean "not curved", except in a non-technical, small-scale practical sense of the term because the Earth's curvature is negilgable on small scales.
Clete