Answer
See the detailed answer below.
Work Step by Step
a) Since the jet plane moves on a horizontal plane (level course), its vertical acceleration component is zero. And since it moves horizontally at a constant velocity, its horizontal acceleration component is also zero.
Thus, the net force exerted on it is zero.
$$\sum F_{jet\;plane}=\color{red}{\bf 0}\;\rm N$$
b) The forces exerted on the jet are shown in the figure below; where $F_B$ is the lifting force (or buoyant force), $F_G$ is the gravitational force, $F_D$ is the drag force, and $F_T$ is the thrust force.
c) When the jet takes a right turn it sinks its right wing, so the buoyant force now has a right component that allows it to take the turn.
As we see in the second figure below, behind the plane we can see its wings. The forces exerted on it at the level (the thrust and the drag) are still the same but the buoyant force changed.
d) When the jet takes a right turn it sinks its right wing, so the buoyant force now has a right component that allows it to take the turn. This right component represents the radio force that allows it to move in a horizontal circle.
