Why don't jet aircrafts fly im the troposphere ?

Jet aircrafts don't fly in the Troposphere because there the gravitational force is very high which attracts the jet toward itself. For this reason the jets and planes flies in the Stratosphere as there the gravitational force is less

Hope it is helpful

Bcos there are only few clouds

Explanation:

Commercial jet aircraft fly in the lower stratosphere to avoid the turbulence which is common in the troposphere below. The stratosphere is very dry; air there contains little water vapor. Because of this, few clouds are found in this layer; almost all clouds occur in the lower, more humid troposphere.

because of friction

i think it is becoz of absence oxygen

i think it is due to the presence of some clouds present in that layer