Airplanes need an atmosphere (aka, ‘air’) to rise up into the sky (aka, ‘fly’), just like a boat needs water to float and move around.

So an airplane could fly on Mars (let’s say it’s battery powered so we can ignore fuel) because Mars has an atmosphere.

But on the Moon an airplane would never be able to lift off of the ground, no matter how fast it was moving, because there is no atmosphere for it to push off of and ‘float’ through (on top of that, but keep in mind it’s a separate issue, turbines and propellers would also be useless on the moon).

Here is a weird fact: Air and water are both considered ‘fluids’, therefore the same principle that lets airplanes fly also works underwater!

Conclusion: Airplanes cannot leave Earth’s atmosphere because they require it to operate, and in more ways than one!