There is no real "High Flying" US airline. Flight altitudes are determined by aircraft type, and Air Traffic Control, with some input by the crew. All US airlines fly at generally the same altitude, assuming the same aircraft. Now internationally, Air France and British Airways fly high because of the Concorde, which cruises somewhere around 60,000 feet. And the SR-71 military sureveillance aircraft flies somewhere around 70,000 feet. Hope this helps.