Delta Airlines continues its impressive recovery from bankruptcy with strong year over year gains in passengers carried and in revenue growth. Delta's traffic rose 5.9% in May overall, with a very strong 2.9 percent growth in domestic traffic. Overall growth was driven by a whopping 12.8 percent growth in international traffic in May.

Having personal experience in dealing with Delta senior management, Delta seems to be a changed airline. Using 6 sigma principals applied to everything from cabin cleanliness to misrouted bags, the airline seems to be in full recovery mode with momentum being felt by passengers. Delta's strategic investment in long haul routes has clearly benefited the airline due to lack of discounters on those routes.

Most airlines have struggled domestically, with even stalwarts like Southwest Airlines openly discussing slowing expansion of their US domestic network.