The density of the air at these levels are too thin, so the wings of the plane would not serve any purpose, since they require lift from the wind. However, the mesosphere does not have this.
The mass of the air also reduces the plane's thrust, or the force that causes the plane to move, or accelerate.
In other words, it would too risky and the elements needed for the plane to fly are not there.
It has a very high Maintenance and set up cost. The technology needed is not yet mature so alot of development is needed. Many rural farmers may loose living and become unemployed
