SB 4.12.30
tadottanapadah putro
dadarsantakam agatam
mrtyor murdhni padam dattva
arurohadbhutam grham
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
When Dhruva Maharaja was attempting to get on the transcendental plane, he saw death personified approach him. Not caring for death, however, he took advantage of the opportunity to put his feet on the head of death, and thus he got up on the airplane, which was as big as a house.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
To take the passing away of a devotee and the passing away of a nondevotee as one and the same is completely misleading. While ascending the transcendental airplane, Dhruva Maharaja suddenly saw death personified before him, but he was not afraid. Instead of death’s giving him trouble, Dhruva Maharaja took advantage of death’s presence and put his feet on the head of death. People with a poor fund of knowledge do not know the difference between the death of a devotee and the death of a nondevotee. In this connection, an example can be given: A cat carries its kittens in its mouth, and it also catches a rat in its mouth. Superficially, the catching of the rat and the kitten appear to be one and the same, but actually they are not. When the cat catches the rat in its mouth it means death for the rat, whereas when the cat catches the kitten, the kitten enjoys it. When Dhruva Maharaja boarded the airplane, he took advantage of the arrival of death personified, who came to offer him obeisances; putting his feet on the head of death, he got up on the unique airplane, which is described here to be as big as a house (grham).
There are many other similar instances in Bhagavata literature. It is stated that when Kardama Muni created an airplane to carry his wife, Devahuti, all over the universe, the airplane was like a big city, carrying many houses, lakes and gardens. Modern scientists have manufactured big airplanes, but they are packed with passengers, who experience all sorts of discomforts while riding in them.
Material scientists are not even perfect in manufacturing a material airplane. In order to compare to the plane used by Kardama or the plane sent from Visnuloka, they must manufacture an airplane equipped like a big city, with all the comforts of life — lakes, gardens, parks, etc. Their plane must be able to fly in outer space and hover, and visit all other planets. If they invent such a plane, they will not have to make different space stations for fuel to travel into outer space. Such a plane would have an unlimited supply of fuel, or, like the plane from Visnuloka, would fly without it.