The reaction force in an airplane is a direct result of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. Here's how it applies to an airplane:

1. Action: The Airplane's Engines Generate Thrust: The airplane's engines push air backwards (action), creating thrust.

2. Reaction: The Air Pushes Back on the Airplane: According to Newton's Third Law, the air pushed backwards by the engines reacts by pushing the airplane forward (reaction). This forward force is what propels the airplane through the air.

3. Action: The Airplane's Wings Create Lift: The airplane's wings are designed to create lift. They are shaped in a way that causes air to flow faster over the top surface than the bottom. This difference in airspeed creates a difference in air pressure, resulting in an upward force called lift.

4. Reaction: The Airplane Pushes Down on the Air: Again, by Newton's Third Law, the airplane pushing down on the air with its wings (action) results in the air pushing back upwards on the airplane (reaction). This upward force is the lift that keeps the airplane in the air.

5. Action: Gravity Pulls the Airplane Down: Gravity constantly pulls the airplane towards the Earth.

6. Reaction: The Airplane Pushes Back on the Earth: Newton's Third Law dictates that the airplane pushing down on the Earth (action) creates a reaction force that pushes the airplane upwards. This force is extremely small compared to the force of gravity, but it does contribute to the overall forces acting on the airplane.

In summary: The reaction forces in an airplane are essential for its flight. They are a direct consequence of the actions taken by the airplane's engines and wings, as dictated by Newton's Third Law of Motion. These forces work together to overcome gravity and allow the airplane to take off, fly, and land.