The third option, stating that both 1 and 2 are correct, is indeed the right answer. Here`s why each statement is true:

1. In the lower stratosphere, there are no clouds or water vapour. Air in higher altitudes, like the stratosphere, is dry because most of the water vapor in the Earth`s atmosphere is found at lower altitudes closer to the surface. The absence of water vapour reduces the possibility of icing on the aircraft, allowing the plane to fly smoothly.

2. There are no vertical winds in the lower stratosphere. Wind patterns in the lower stratosphere are generally horizontal and do not include convective currents or violent disturbances like storms, all of which could create vertical winds. This absence of vertical winds further provides a smooth flight for jet aircrafts.

In conclusion, due to both these factors, jet aircrafts can fly easily and smoothly in the lower stratosphere.