In the world of Ivalice you can become a large variety of things; mechant, trader, shopowner, soldier, miner, researcher, barkeep, hunter and many more. Balthier however chose to become a pirate, a Sky Pirate. An occupation that isn't all unrespected by the people. Many youngsters, including Vaan and the other orphans who spend their days down in Lowtown of Rabanastre, look up to the sky pirates and dream to someday have an airship of their own to freely roam the world in.
The upside of sky pirating is of course the freedom. Not everyone can afford to buy a pair of wings and Ivalice is a huge world inviting to adventure. On the other hand, plundering doesn't earn you much popularity with those who are bestolen and can get one or two bounty hunters on your heals.

The sky pirates seem scarce in numbers but later in the game, we learn that there is a city filled with pirates both of the sky and of the sea, which kind of surprised me. This place is called Balfonheim Port and is run by the sky pirate Reddas. Aspiring pirates come to Balfonheim to learn the trade but many end up working as cargoloaders. The resident Lofty Sky Pirate in the Port says;

"Me and me mates are off to make us a pretty gil. What? Now, don't get me wrong... all we do is ship cargo, you see. That pirate moniker is more of a tradition than a description."

In the game's bestiary file #99 Redmaw you will find Sage Knowledge #6: Sky Pirates. It reads;

"Sky Pirates A name for the free folk who ply the open skies in airships. Though they are collectively called "pirates," their actual occupations vary by individual.Some search for legendary treasures, some merely travel the world, while others are indeed ruthless villains who attack trade ships and plunder goods for profit. In recent years, the Archadian Empire has stepped up patrols, bringing the worst of the lot, all but consigning the more flamboyant feats of piracy to history. Of late, many are the pirates who have given up the thief's life for that of the headhunter, bringing their former comrades-in-arms to justice... for a bounty. Those few who remain pirates have struggled hard to retain the title, and are duly proud of it."

Balthier is described like a kind of Robin Hoodesque pirate who only steals from those who deserve it. But his motives aren't fame or excitement, but the reason for choosing this type of life lies in his past.