Cordle's firm estimates that without the merger, the five current legacy carriers -- Delta-Northwest, American, United, Continental and US Airways -- face $20 billion in additional costs by 2014 from rising fuel prices, airport facility charges and security and labor hikes. The United-Continental merger should allow those airlines alone to save $3 billion in such costs, he said.

    Even one of the industry's low-cost competitors welcomes the merger. Virginia Gambale, a director at JetBlue, said the company is pleased with the deal, noting that the industry's fragile state and mercurial fortunes make it difficult to engage in long-term planning. "As we deal with less players in the market, it makes it easier to decide where and how we will compete," she said. "Uncertainty breeds its own inefficiency."