a navigator is an officer, who is responsible for navigation. It can be part of a crew or flight crew. In particular in aviation the occupation became extinct however so well, since the airplanes for navigation were equipped with Flight management systems, so that the pilots can implement navigation without support of a navigator. On large ships however one finds this very day navigators.
In the Russian airplanes of older design the navigator is further on board and equipped with substantially more authority than in western airplanes. It can give instructions here to the pilot, as long as no air emergency arises, while in western airplanes the navigator is subordinated to the pilot.