When the external force on a system of bodies is zero, then the total linear momentum of the system of bodies remains constant (in time and space). ... The rate of change in the momentum of hot gases downward direction, is equal to the rate of change in momentum of the rest of rocket in vertically upward direction.

Answer: the areoplane and rockets fly as per as the law of conservation of momentum as the law say that every object that moves upward again comes down due to gravitional force but due to the areondynamic design they are able to fly.

Explanation:as bird can also be pulled by the gravitional force but due to their aerodynamic design and continuous flapping of their wings they Are able to fly similarly plane has been designed aero dynamic and dye to their turbo propeller they are able to continuously fly till the fuel ends but in rocket their are some difference the rocket is also designed areo dynamic but due to the booster alarge amount of energy is being used to push the rocket upward to a high point that where the power of gravity is low and I'd not enough to take the rocket to its atmosphere.

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