Airworthiness is a big word that means whether or not an airplane is safe to fly. Just like when you ride your bike or scooter, you want to make sure everything is working well, airplanes need to be checked and tested to make sure they are ready to fly, and that they will be able to fly safely.
In order to make sure an airplane is airworthy, the people who build the airplane and those who repair and maintain it have to follow certain rules and regulations. These rules and regulations are set by flight safety organizations like the Federal Aviation Administration (FAA), and they make sure that each airplane is checked, tested, and maintained at specific intervals so that it is always safe to fly.
The people who work on airplanes are called mechanics, and they are like doctors for airplanes. They check and fix the parts and systems of the airplane, from the engines to the wings to the electronics, to make sure they are all in good working order. They also use special tools and equipment to run tests and inspections that help them find any problems or potential problems, and then they fix them right away.
Before an airplane can take off, a special inspection has to happen called a pre-flight inspection. The pilot or another qualified person checks everything from the engine to the propellers to the brakes to make sure they are all working properly. After that, the airplane can take off and fly safely, knowing that everyone who worked on it did everything they could to make sure it is airworthy.