The jet aircrafts fly very easily and smoothly in the lower stratosphere. What could be the appropriate explanation?

1. There are no clouds or water vapour in the lower stratosphere.
2. There are no vertical winds in the lower stratosphere.

Which of the statements given above is/are correct in this context?

Commercial airliners typically cruise in the lower reaches of the stratosphere. Because the temperature in the tropopause and lower stratosphere remains constant (or slightly increases) with increasing altitude, there is very little convective turbulence or vertical wind at these altitudes. There is no dust particles and water vapour in the lower stratosphere. Hence, weather phenomenon doesn't take place in lower stratosphere. Stratosphere contains ozone layer, which absorbs ultra-violet radiation.