The phrase has origins with Virgil, who wrote in his Aeneid: "sic itur ad astra" ('thus one journeys to the stars')[1] and "opta ardua pennis astra sequi" ('desire to pursue the high[/hard to reach] stars on wings').
[2] Another origin is Seneca the Younger, who wrote in Hercules: "non est ad astra mollis e terris via" ('there is no easy way from the earth to the stars').
[4] Astra is the accusative plural form of the Latin word astrum 'star' (from Ancient Greek ἄστρον astron 'star', from Proto-Indo-European *h₂ster-).
[5] Ad astra is used as, or as part of, the motto of many organizations, most prominently, air forces.
It has also been adopted as a proper name for various unrelated things (publications, bands, video games, etc.).