Thick clouds are really just a light mist, flying through them is similar to driving through thick fog, it doesn't affect the performance of the aircraft in the least.
It does however affect the pilots ability to see, and most aircraft are equipped with instrumentation which allows the pilot to maintain control and positional awareness even with all windows blotted out. Aircraft which are not so equipped are forbidden from flying into clouds. Aircraft flying into and through clouds can only do so under more restrictive rules requiring constant contact with air-traffic-control.
They don't 'bump' into them ! Clouds are not solid - so planes simply fly through them !
radar
They don't always fly above the clouds. They fly below, in or above them. Planes have optimum levels that they fly at. Sometimes that may be above the clouds, but not always.
When a pilot has to fly through thick clouds, many instruments come into play. These instruments help the pilot navigate the clouds and are known as GPS and Distance Measuring Equipment which prevents collisions in mid air during these weather conditions.
Artificial horizon [for pitch and roll information.] Airspeed indicator [to keep from diving/and or slowing to a stall situation] Turn and bank indicator [for making turns and the use of proper rudder input to keep the aircraft from skidding]
They can fly but they have a high chance of getting damaged.
Yes, and planes frequently do. Clouds are only made of water droplets which are quite small, and even when it is raining they can be easily passed through. Aircraft do, however, avoid flying through cumulonimbus clouds because they are associated with turbulent air, ice and updrafts.
Of course, planes can fly.
No. The surface of Venus is obscured by thick clouds. If you could fly above the clouds then you would see the same stars that you see from Earth.
Some airplanes do, but it very risky.
Clouds aren't solid. You can just pass through them (or fly through them).
The Great Plains are the stretch of land that runs through the Midwest of the United States. Make sure you spell it plains not planes because planes are the things that fly through the air!