What is the length of any airplane?

The problem is that there are literally thousands of different kinds of airplanes, and they are all different sizes.

There have been (real, not model) sport airplanes not much more than 10 feet (3 meters, or 300 cm) in length.

The largest airplane in the world is the Antonov AN-225, which is 275.6 feet, or 84 meters (8,400 cm) long.

To get a little clearer view of the context of your question, take a look at this: