A cargo airline is like a big airplane that carries things instead of people. Just like how you pack a suitcase when you go on a trip, people and companies also pack things in boxes and crates when they need to send them to another place far away.
But sometimes these things are too big or heavy to fit on a regular airplane that carries people. That's where a cargo airline comes in.
The cargo airline has big planes that are specially designed to carry these heavy things. They have a lot of room inside, so they can fit a lot of boxes and crates in there. They also have special loading doors that make it easy to get these heavy boxes and crates on and off the plane.
Once all of the boxes and crates are loaded onto the cargo airline's plane, it takes off and flies to the place where the boxes and crates need to go. Sometimes it flies to other countries, so it can take a long time to get there.
When the cargo airline's plane finally reaches its destination, it lands and the boxes and crates are unloaded. Then, they are sent to the people or companies who were waiting for them.
So, basically, a cargo airline is like a big truck that flies in the sky and carries really heavy things from one place to another.