SB 4.6.27

tāra-hema-mahāratna-
 vimāna-śata-saṅkulām
juṣṭāṁ puṇyajana-strībhir
 yathā khaṁ sataḍid-ghanam
Synonyms: 
tāra-hema — of pearls and gold; mahā-ratna — valuable jewels; vimāna — of airplanes; śata — with hundreds; saṅkulām — crowded; juṣṭām — occupied, enjoyed; puṇyajana-strībhiḥ — by the wives of the Yakṣas; yathā — as; kham — the sky; sa-taḍit-ghanam — with the lightning and the clouds.
Translation: 
The airplanes of the heavenly denizens are bedecked with pearls, gold and many valuable jewels. The heavenly denizens are compared to clouds in the sky decorated with occasional flashes of electric lightning.
Purport: 

The airplanes described in this verse are different from the airplanes of which we have experience. In the Śrīmad-Bhāgavatam and all the Vedic literatures, there are many descriptions of vimāna, which means “airplanes.” On different planets there are different kinds of airplanes. On this gross planet earth, there are airplanes run by machine, but on other planets the airplanes are run not by machine but by mantric hymns. They are also used especially for enjoyment by the denizens of the heavenly planets so that they can go from one planet to another. On other planets which are called Siddhalokas, the denizens can travel from one planet to another without airplanes. The beautiful airplanes from the heavenly planets are compared here to the sky because they fly in the sky; the passengers are compared to the clouds. The beautiful damsels, the wives of the denizens of the heavenly planets, are compared to lightning. In summation, the airplanes with their passengers which came from higher planets to Kailāsa were very pleasant to look at.