Mal:

"Okay, clearly some aptitude for the....but it ain't all buttons and charts, Little Albatross. You know what the first rule of flying is? Well, I suppose you do, since you already know what I'm about to say."

River:

"I do. But I like to hear you say it."

Mal:

"Love. You can learn all the math in the 'Verse, but you take a boat in the air you don't love, She'll shake you off just as sure as the turning of worlds. Love keeps her in the air when she ought to fall down, Tells you when she's hurting 'fore she keens. Makes her a home."

-Serenity