Ever since Final Fantasy III, summons are a mainstay, and then staple, of the Final Fantasy franchise. The regulars (Ifrit, Shiva, Bahamut, etc.) all make appearances throughout the Final Fantasy series. But they’re absent in Final Fantasy XII. Instead, Lucavi replaces them as Espers. From what we know, the Lucavi eventually run rampage and destroy most Ivalice. As for the familiar summons?
But what powers the airships? They’re “Skystones”, which are a type of magicite. It’s a common theme in Final Fantasy for the inhabitants to not fully understand the ancient power their technology possesses. After the Lucavi went on a rampage, destroying Ivalice’s technology, summoners studied Skystone in a different light. Summoners could conjure Espers with the Skystones. In this sense, the airships housed the ancient powers of Ramuh, Shiva, Ifrit and others. The twelve Archadian ships are:
When Vayne merged with Bahamut his nethicite combined with the skystone, creating a super-summon. Caius merged with Bahamut in Final Fantasy XIII-2 in a slightly different process. Ivalice’s inhabitants have the powers to become gods unbeknownst to them all along.