Gravitational force on aircraft at some distance from the Earth is given as

here we know that
= mass of Earth
= mass of aircraft
r = distance between center of earth and aircraft
now as the aircraft is flying away from the surface of Earth so here the distance between them is increasing with the motion of aircraft
So as it moves away the force between them will decrease
So here we can say that
When a spacecraft travels away from Earth, the gravitational force acting on it
decreases