The Vaikuntha airplane does not move by mechanical arrangement. There are three processes for moving in outer space. One of the processes is known to the modern scientist. It is called ka-pota-vayu. Ka means outer space, and pota means ship. There is a second process also called kapota-vayu. Kapota means pigeon. One can train pigeons to carry one into outer space. The third process is very subtle. It is called akasa-patana. This akasa-patana system is also material. Just as the mind can fly anywhere one likes without mechanical arrangement, so the akasa-patana airplane can fly at the speed of mind. Beyond this akasa-patana system is the Vaikuntha process, which is completely spiritual. The airplane sent by Lord Visnu to carry Dhruva Maharaja to Sisumara was a completely spiritual, transcendental airplane. Material scientists can neither see such vehicles nor imagine how they fly in the air. The material scientist has no information about the spiritual sky, although it is mentioned in the Bhagavad-gita (paras tasmat tu bhavo nyah [Bg. 8.20]).