The gods got tired of the different people fighting and warring and committing atrocities on each other so they broke the world. Every other species in the world suddenly disappeared, except Elves.

This was seen as wonderful at first... but they missed what the other species traded/exported. The Dwarven metal. The Humans' grain. The Kobolds' glass-blowing.

The Elves investigated and found that the other species still existed-- elsewhere. Magic was applied, and it was found that the species' other worlds were accessible through the elemental plane of Air.

And so, Airships were built, of Elven timber, and they began to trade...

--Elves have timber and paper
--Dwarves have metal and flint
--Aaracokra have gunpowder and rum
--Humans have food (and beeswax) and textiles/dye
--Lizardmen have water (and salt) and oil (and fish)
--Gnolls have leather and spices
--Kobolds have Glass and ceramics

And eventually, everyone had ships for trading through the Plane of Air.

Although the Gnolls had a flying Bullette, and the Lizardmen rode on the back of a really giant turtle.

So, yeah, that led to the airship pirates...