Here are three simple ways to say that idea for a 6-year-old:
- Brave people fly in airplanes. By flying, they can go far and fast to bring help or a package to someone who needs it.
- Some brave people ride in flying machines. From the sky they can reach faraway places quickly to deliver help or a package.
- Pilots are brave and fly planes to get to faraway places quickly and bring help or a package.
How I changed it: I fixed 'By air' to 'By flying', used simple words like 'fly', 'airplanes', 'help', and kept the sentences short so they are easy to understand.