(CNN) -- What makes airline passengers happy? Sometimes it's as simple as a smile. Along with mobile check-in, Wi-Fi in the air and other technological advances, the simple act of airline employees smiling is increasing airline passenger satisfaction. Airline passenger satisfaction has improved to its highest levels since 2006, according to J.D Power & Associates' 2013 North America Airline Satisfaction Study released Wednesday. U.S. airlines collect $6 billion in fees "Traditional carriers have improved significantly across the entire passenger experience, and it is a positive sign to see them turn a corner and starting to rise again, even as there is still more opportunity to improve," said Jessica McGregor, senior manager of J.D. Power's global travel and hospitality practice. "While satisfaction with low-cost carriers only slightly improves, greater gains in the rest of the experience are masked by lower passenger satisfaction with cost and fees."
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JetBlue tops airline satisfaction study for ninth consecutive year
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Passengers who use in-flight Wi-Fi report more satisfaction with their airline
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An employee smile or two (or more) makes passengers even happier
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Fliers still dislike bag fees but not as much as they did last year
@placeholder also earned the top score among low-cost carriers for the eighth year in a row.