A vimana is a word with several meanings ranging from temple or palace to mythological flying machines described in Sanskrit epics. References to these flying machines are commonplace in ancient Indian texts, even describing their use in warfare. As well as being able to fly within Earth's atmosphere, vimanas were also said to be able to travel into space and travel under water.

Descriptions in the Vedas and later Indian literature detail vimanas of various shapes and sizes:
In the Vedas: the Sun and Indra and several other Vedic deities are transported by flying wheeled chariots pulled by animals, usually horses (but the Vedic god Pusan's chariot is pulled by goats).The "agnihotra-vimana" with two engines. (Agni means fire in Sanskrit.) The "gaja-vimana" with more engines. (Gaja means elephant in Sanskrit.) Other types named after the kingfisher, ibis, and other animals.

The word comes from Sanskrit and seems to be vi-mana = 'apart' or 'having been measured". The word also means a part of a Hindu temple. The meaning of the word likely changed in this sequence:
An area of land measured out and set apart to be used for sacred purposes.
Temple - A god's palace
In the Ramayana: the demon-lord Ravana's flying palace called Pushpaka.
In later Indian writings: other flying vehicles, and sometimes as a poetic word for ordinary ground vehicles. In some modern Indian languages, the word vimana means ordinary real aircraft.

The Buddhist book Vimanavatthu (Pali for "Vimana Stories") uses the word "vimana" with a different meaning: "a small piece of text used as the inspiration for a Buddhist sermon".

Sanskrit texts are filled with references to gods who fought battles in the sky using vimanas equipped with weapons as deadly as any we can deploy in these more enlightened times.

In the Ramayana there is a passage in the Ramayana which reads:
"The Pushpaka chariot that resembles the Sun and belongs to my brother was brought by the powerful Ravana; that aerial and excellent car going everywhere at will .... that car resembling a bright cloud in the sky ... and the King [Rama] got in, and the excellent car at the command of the Raghira, rose up into the higher atmosphere.'"

"Pushpaka" is Sanskrit for "flowery". It is the first flying vimana mentioned in Hindu mythology (as distinct from gods' flying horse-drawn chariots). It is also called Pushpaka Vimana.

The special characteristic of this vehicle is, "What ever may be the number of people sitting in it, always there will be one more seat vacant i.e., If N people sit, There will be (N+1) seats". It was basically a vehicle that could soar the skies for long distances. It shows that even in ancient times, people were curious about flight and might have tried to design flying vehicles.

Pushpaka was originally made by Maya for Kubera, the God of wealth, but was later stolen, along with Lanka, by his half-brother, the demon king Ravana.

The core epic of the Mahabharata mentions no vimanas, but vimanas often occur in the large amount of matter which was added to the Mahabharata corpus later. One example is that the Asura Maya had a Vimana measuring twelve cubits in circumference, with four strong wheels.

The Mahabharata is a veritable gold mine of information relating to conflicts between gods who are said to have settled their differences apparently using weapons as lethal as those we have now. Apart from 'blazing missiles', the poem records the use of other deadly weapons. 'Indra's Dart' (Indravajra) operated via a circular 'reflector'. When switched on, it produced a 'shaft of light' which, when focused on any target, immediately 'consumed it with its power'.

In one exchange, the hero, Krishna, is pursuing his enemy, Salva, in the sky, when Salva's Vimana, the Saubha, is made invisible in some way. Undeterred, Krishna immediately fires off a special weapon: "I quickly laid on an arrow, which killed by seeking out sound". Many other terrible weapons are described, quite matter-of-factly, in the Mahabharata, but the most fearsome of all is the one used against the Vrishis. The narrative records:

"Gurkha flying in his swift and powerful Vimana hurled against the three cities of the Vrishis and Andhakas a single projectile charged with all the power of the Universe. An incandescent column of smoke and fire, as brilliant as ten thousands suns, rose in all its splendour. It was the unknown weapon, the Iron Thunderbolt, a gigantic messenger of death which reduced to ashes the entire race of the Vrishnis and Andhakas."

It is important to note, that these kinds of records are not isolated. They can be cross-correlated with similar reports in other ancient civilizations. The after-affects of this Iron Thunderbolt have an ominously recognizable ring. Apparently, those killed by it were said to be so burnt that their corpses were unidentifiable. The survivors fared little better, as it caused their hair and nails to fall out.

Perhaps the most disturbing and challenging, information about these allegedly mythical Vimanas in the ancient records is that there are some matter-of-fact records, describing how to build one. In their way, the instructions are quite precise.

The Mahabharata also tells of the awesome destructiveness of the war: "... (the weapon was) a single projectile charged with all the power of the Universe. An incandescent column of smoke and flame as bright as the thousand suns rose in all its splendor... An iron thunderbolt, a gigantic messenger of death, which reduced to ashes the entire race of the Vrishnis and the Andhakas.... the corpses were so burned as to be unrecognizable. The hair and nails fell out; pottery broke without apparent cause, and the birds turned white.... after a few hours all foodstuffs were infected.... to escape from this fire, the soldiers threw themselves in streams to wash themselves and their equipment..." Some say that the Mahabharata is describing an atomic war. References like this one are not isolated; but battles, using a fantastic array of weapons and aerial vehicles are common in all the epic Indian books. One even describes a Vimana-Vailix battle on the Moon! The above section very accurately describes what an atomic explosion would look like and the effects of the radioactivity on the population. Jumping into water is the only respite.

In the Sanskrit Samarangana Sutradhara (Literally, "controller of the battlefield"), it is written:

"Strong and durable must the body of the Vimana be made, like a great flying bird of light material. Inside one must put the mercury engine with its iron heating apparatus underneath. By means of the power latent in the mercury which sets the driving whirlwind in motion, a man sitting inside may travel a great distance in the sky. The movements of the Vimana are such that it can vertically ascend, vertically descend, move slanting forwards and backwards. With the help of the machines human beings can fly in the air and heavenly beings can come down to earth."