Answer :
1. The oceans and the atmosphere are the two large reservoirs of water in the Earth's hydrologic cycle. The two systems are complexly linked to one another and are responsible for Earth's weather and climate. The oceans help to regulate temperature in the lower part of the atmosphere. The atmosphere is in large part responsible for the circulation of ocean water through waves and currents. However, the ocean is primarily a liquid and the atmosphere is mostly gas, so they are different states of matter.
2. The main reason airplanes fly in the stratosphere is because this is where the least amount of turbulence is found. In addition, because the stratosphere is very dry, there are fewer clouds in this layer, making for a much smoother ride overall. It is simply the perfect layer to fly in for a number of reasons. Flying higher than the stratosphere will again cause disturbances.