It's been surmised by flat-earthers that if the Earth is moving then we should be able to lift off of the ground in a balloon and the ground should travel below us. Others have suggested that flights going with the rotation of the globe should be impossible because the globe rotates at 1000 mph but planes only fly at about 500 mph. These theories are both part of the same false premise which is that as soon as we leave the ground we should cease to travel in the same direction and speed as the Earth.
It's hard to believe some of the silly demonstrations thought up to prove the Earth is flat. One recent demonstration that has been filmed by a number of guys is bringing a spirit level (bubble level) on a plane and looking for the device to show the nose of the plane pointing down. Roll your eyes all you want, but this is a real test that some people take seriously. Below I will describe exactly why this test won't work.