Srimad Bhagavatam Canto 04, Chapter 12, Text 27

SB 4.12.27

etad vimana-pravaram
upasthapitam ayusmann
adhirodhum tvam arhasi
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
O immortal one, this unique airplane has been sent by the Supreme Personality of Godhead, who is worshiped by selected prayers and who is the chief of all living entities. You are quite worthy to board such a plane.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
According to astronomical calculation, along with the polestar there is another star, which is called Sisumara, where Lord Visnu, who is in charge of the maintenance of this material world, resides. Sisumara or Dhruvaloka can never be reached by anyone but the Vaisnavas, as will be described by the following slokas. The associates of Lord Visnu brought the special airplane for Dhruva Maharaja and then informed him that Lord Visnu had especially sent this airplane.
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 also 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).
Srimad Bhagavatam Canto 04, Chapter 12, Text 26
Srimad Bhagavatam Canto 04, Chapter 12, Text 28