At a recent investor conference, WestJet CFO Vito Culmone said the airline was considering a section of roomier and more expensive “premium economy” seats on some of its Boeing 737s. It might seem risky to tinker with WestJet’s ultra-successful all-economy formula, but airlines around the world—including Virgin Atlantic, Delta Air Lines and Cathay Pacific—have identified a lucrative market: people who can’t afford to pay thousands of dollars for full-blown business class, yet can’t bear the thought of sitting in cramped coach. Ranging in price from a few hundred to $1,000 more than a standard economy class seat, a “premium economy” ticket usually guarantees more legroom and, depending on the airline, wider seats and a separate cabin, as is the case with Air France’s “Premium Voyageur” seats. The best part? Some airlines say their premium economy sections—which take up far less pricey cabin real estate than business class—are becoming the most profitable areas in their planes.