Which aircraft has visited Neptune till now?

It is Voyager 2 that was launched in 1977. This is known to be a type of probe that will be used to study the different planets that are available in the solar system. This is successful in reaching the planets that are harder to reach because of their distance from earth.

Take note that because of the distance, it will be hard to monitor Neptune closely. In fact, the only time that it was visited up close was on August 25, 1989. The spacecraft was only 3000 kilometers away from the northern portion of the planet. This has not been imitated by other spacecraft ever since.