Cid is just a pilot who has a dream to go to space. It seems he'll never fufill his dream, but he's pretty helpful in the game. He seems the rudest and crudest of all people, but inside, he's really kind and cares a lot about others. His old ship, a Shinra ship, failed flying to space because of his wife, and he still blames her by bossing her around. But she's such a loving and caring wife, she doesn't even care! Cid is the world guines of mechanics, wether it be of sea or of air or of land; he knows it all. He's a proud ally of Cloud's, and helps out a lot by controling Highwind, and instructing Cloud on other vehicles and difficult machines.
Cid is one of the best to have in your party. He has a fair amount of HP and MP compared to level; about the same HP as compared to Cloud, really. And, often enough, you'll find great weapons worth keeping for Cid's use along the way. And with his ultimate weapon on, he attacks for about 9000 points, even at level 50. I like to use him often; and it's just my advice to.