Refers to a person who flies or operates an aircraft. In everyday speech パイロット is also very common; 飛行士 has a slightly more written or occupational feel.
Since childhood, she had dreamed of becoming a pilot.
経験豊かな飛行士が小型機を操縦した。
An experienced pilot flew the small aircraft.
He became a pilot, fulfilling his long-held dream.
My older sister works as a pilot for an airline.