5. Why don’t airplanes fly through cumulonimbus clouds?
6. How is lightning formed?
7. Why do you always see the lightning before you hear the thunder?
8. If you hear the thunder 25 seconds after you see the lightning, how far away is the thunderstorm?

5. Cumulonimbus Clouds are the most hazardous clouds a plane can get in. Turbulence is rarely fatal or catastrophic on bigger airplanes and even for the smaller single engines, but icing can be much more disastrous for all types of airplanes regardless.  

6. Lightning is an electric current. Within a thundercloud way up in the sky, many small bits of ice (frozen raindrops) bump into each other as they move around in the air. All of those collisions create an electric charge. After a while, the whole cloud fills up with electrical charges.

7. The speed of light (299 792 458 m / s)  is faster than the speed of sound (343 m / s).

8.  5 miles away (divide it by 5. Five second is one mile.)