After this, the inhabitants of Siddhaloka, as well as the inhabitants of Vidyādhara-loka, transformed the great sage Kapila into a calf, and making the whole sky into a pot, they milked out specific yogic mystic powers, beginning with aṇimā. Indeed, the inhabitants of Vidyādhara-loka acquired the art of flying in the sky.
The inhabitants of both Siddhaloka and Vidyādhara-loka are naturally endowed with mystic yogic powers by which they not only can fly in outer space without a vehicle but can also fly from one planet to another simply by exerting their will. Just as fish can swim within water, the residents of Vidyādhara-loka can swim in the ocean of air. As far as the inhabitants of Siddhaloka are concerned, they are endowed with all mystic powers. The yogīs in this planet practice the eightfold yogic mysticism—namely yama, niyama, āsana, prāṇāyāma, pratyāhāra, dhāraṇā, dhyāna and samādhi. By regularly practicing the yogic processes one after another, the yogīs attain various perfections; they can become smaller than the smallest, heavier than the heaviest, etc. They can even manufacture a planet, get whatever they like and control whatever man they want. All the residents of Siddhaloka are naturally endowed with these mystic yogic powers. It is certainly a very wonderful thing if we see a person on this planet flying in the sky without a vehicle, but in Vidyādhara-loka such flying is as commonplace as a bird's flying in the sky. Similarly, in Siddhaloka all the inhabitants are great yogīs, perfect in mystic powers.
The name of Kapila Muni is significant in this verse because He was the expounder of the Sāṅkhya philosophical system, and His father, Kardama Muni, was a great yogī and mystic. Indeed, Kardama Muni prepared a great airplane, which was as large as a small town and had various gardens, palatial buildings, servants and maidservants. With all this paraphernalia, Kapiladeva's mother, Devahūti, and His father, Kardama Muni, traveled all over the universes and visited different planets.
(Srimad Bhagavatam------4:18:19------purport).

As Lord Brahmā descended on his carrier, the great swan, all the residents of the planets named Siddhaloka, Gandharvaloka, Sādhyaloka and Cāraṇaloka, as well as great sages and demigods flying in their different airplanes, assembled within the canopy of the sky to receive Lord Brahmā and worship him. As he received respect and adoration from the residents of the various planets, Lord Brahmā appeared just like the full moon surrounded by illuminating stars. Lord Brahmā's great swan then arrived at the border of Gandhamādana Hill and approached Prince Priyavrata, who was sitting there.
It appears from this description that there is regular interplanetary travel between the planets of the demigods. Another significant point is that there is a planet covered mostly by great mountains, one of which is Gandhamādana Hill. Three great personalities—Priyavrata, Nārada and Svāyambhuva Manu—were sitting on this hill. According to Brahmā-saṁhitā, each universe is filled with different planetary systems, and every system has a unique opulence. For example, on Siddhaloka, all the residents are very advanced in the powers of mystic yoga. They can fly from one planet to another without airplanes or other flying machines. Similarly, the residents of Gandharvaloka are expert in musical science, and those on Sādhyaloka are all great saints. The interplanetary system undoubtedly exists, and residents of different planets may go from one to another. On this earth, however, we have not invented any machine that can go directly from one planet to another, although an unsuccessful attempt has been made to go directly to the moon.
(Srimad Bhagavatam------5:1:8------purport).

Sārvabhauma Bhaṭṭācārya replied, "The awakening of pure love of Godhead, which is the result of devotional service, far surpasses liberation from material bondage. For those averse to devotional service, merging into the Brahman effulgence is a kind of punishment."
In the Brahmāṇḍa Purāṇa it is said:
siddha-lokas tu tamasaḥ pāre yatra vasanti hi
siddhā brahma-sukhe magnā daityāś ca hariṇā hatāḥ
"In Siddhaloka (Brahmaloka) there live two kinds of living entities—those who are killed by the Supreme Personality of Godhead due to their having been demons in their previous lives and those who are very fond of enjoying the impersonal effulgence of the Lord." The word tamasaḥ means "the coverings of the universe." Layers of material elements cover the universe, and outside these coverings is the impersonal Brahman effulgence. If one is destined to remain in the Lord's impersonal effulgence, he misses the opportunity to render service to the Personality of Godhead. Therefore devotees consider remaining in the impersonal Brahman effulgence a kind of punishment. Sometimes devotees think of merging into the Brahman effulgence, and consequently they are promoted to Siddhaloka.
(Sri Caitanya Caritamrta------2:6:263------translation and purport).

The great sage Maitreya continued: The supreme devotee, the great saint Nārada, thus explained to King Prācīnabarhi the constitutional position of the Supreme Personality of Godhead and the living entity. After giving an invitation to the King, Nārada Muni left to return to Siddhaloka.Siddhaloka and Brahmaloka are both within the same planetary system. Brahmaloka is understood to be the highest planet within this universe. Siddhaloka is considered to be one of the satellites of Brahmaloka. The inhabitants of Siddhaloka have all the powers of yogic mysticism. From this verse it appears that the great sage Nārada is an inhabitant of Siddhaloka, although he travels to all the planetary systems. All the residents of Siddhaloka are spacemen, and they can travel in space without mechanical help. The residents of Siddhaloka can go from one planet to another individually by virtue of their yogic perfection. After giving instructions to the great King Prācīnabarhi, Nārada Muni departed and also invited him to Siddhaloka.
(Srimad Bhagavatam------4:29:80------purport).

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.
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.
(Srimad Bhagavatam------4:6:27------purport).

As explained in the Second Canto of Śrīmad-Bhāgavatam, the Siddhas are inhabitants of Siddhaloka, where the residents travel in space without vehicles. At their mere will they can pass from one planet to another without difficulty. Therefore, in the upper planets the inhabitants are far superior to the inhabitants of this planet in all matters of art, culture and science, since they possess brains superior to those of human beings. The spirits and jinn mentioned in this connection are also counted among the demigods because they are able to perform uncommon functions not possible for men.
(Srimad Bhagavatam------3:10:28-29------purport).

This statement is from the Siddhas, the inhabitants of Siddhaloka, where the eight kinds of material perfection are complete. The residents of Siddhaloka have full control in the eight kinds of yogic perfection, but from their statement it appears that they are pure devotees. They always merge in the nectarean river of hearing of the pastimes of the Lord. Hearing of the pastimes of the Lord is called kṛṣṇa-kathā. Similarly, there is a statement by Prahlāda Mahārāja that those who are always merged in the ocean of the nectar of describing the Lord's pastimes are liberated and have no fear of the material condition of life. The Siddhas say that the mind of an ordinary person is full of anxieties. The example is given of the elephant who has suffered in a forest fire and who enters into a river for relief.
(Srimad Bhagavatam------4:7:35------purport).

"There are ninety million demigods and seventy million sages, who are all called nārāyaṇāyana, devotees of Lord Nārāyaṇa. Among them, only a few are called nārāyaṇa-parāyaṇa."
nārāyaṇāyanā devā
ṛṣy-ādyās tat-parāyaṇāḥ
brahmādyāḥ kecanaiva syuḥ
siddho yogya-sukhaṁ labhan
The difference between the siddhas and nārāyaṇa-parāyaṇas is that direct devotees are called nārāyaṇa-parāyaṇas whereas those who perform various types of mystic yoga are called siddhas.
(Srimad Bhagavatam------6:14:5------purport).

"Out of many thousands among men, one may endeavor for perfection, and of those who have achieved perfection, hardly one knows Me in truth." The yogīs and jñānīs—that is, the mystic yogīs and the impersonalists—can understand the Absolute Truth as impersonal or localized, but although such realized souls are above ordinary human beings, they cannot understand how the Supreme Absolute Truth can be a person. Therefore it is said that out of many siddhas, the souls who have already realized the Absolute Truth, one may understand Kṛṣṇa, who exactly resembles a human being (narākṛti). This human form was explained by Kṛṣṇa Himself after He manifested the virāṭ-rūpa. The virāṭ-rūpa is not the original form of the Lord; the Lord's original form is Dvibhuja-śyāmasundara, Muralīdhara, the Lord with two hands, playing a flute (yaṁ śyāmasundaram acintya-guṇa-svarūpam). The Lord's forms are proof of His inconceivable qualities.
(Srimad Bhagavatam------9:23:20-21------purport).

As it is said, vṛndāvanaṁ parityajya padam ekaṁ na gacchati: Kṛṣṇa does not leave Vṛndāvana even for a moment. The vṛndāvana-vāsīs—mother Yaśodā, Kṛṣṇa's friends and Kṛṣṇa's conjugal lovers, the younger gopīs with whom He dances—have very intimate relationships with Kṛṣṇa, and if one follows in the footsteps of these devotees, Kṛṣṇa is available. Although the nitya-siddha expansions of Kṛṣṇa always remain with Kṛṣṇa, if those engaged in sādhana-siddhi follow in the footsteps of Kṛṣṇa's nitya-siddha associates, such sādhana-siddhas also can easily attain Kṛṣṇa without difficulty. But there are those who are attached to bodily concepts of life. Lord Brahmā and Lord Śiva, for example, have very prestigious positions, and thus they have the sense of being very exalted īśvaras. In other words, because Lord Brahmā and Lord Śiva are guṇa-avatāras and have exalted positions, they have some small sense of being like Kṛṣṇa. But the pure devotees who inhabit Vṛndāvana do not possess any bodily conception.
(Srimad Bhagavatam------10:9:21------purport).

The Siddhas, the inhabitants of Siddhaloka (where all are born with fully developed mystic powers), and the Cāraṇas, the inhabitants of a similar planet, pray to Kṛṣṇa as follows: "My Lord Govinda, the goddess of learning is decorated with fourteen kinds of educational ornaments, her intelligence is all-pervading within the four departments of the Vedas, her attention is always on the lawbooks given by great sages like Manu, and she is appareled in six kinds of expert knowledge—namely Vedic evidence, grammar, astrology, rhetoric, vocabulary and logic. Her constant friends are the supplements of the Vedas, the Purāṇas, and she is decorated with the final conclusion of all education. And now she has acquired an opportunity to sit with You as a class friend in school, and she is now engaged in Your service."
(Nectar of Devotion).