Minutes before boarding begins for a flight from Dallas to Houston, it’s library quiet inside the terminal. No testy TSA agents yell out instructions. No overhead announcements drone on endlessly about limited overhead space. The loudest noise is the click-clack of a flight attendant’s heels on the concrete floor as she walks by two dozen passengers reclining on cushy couches and chairs.It’s so serene that even Alex Wilcox, CEO of the airline, seems surprised that a departure is imminent. “Oh, I guess people are checking in,” he says as a couple rolls bags past him. They’ve just dropped off their car keys at the valet outside the private hangar at Love Field.All this calm comes at a cost. The airline, Dallas-based JSX, charges business-class fares…