"The second quarter began as a severe challenge for United and the industry as a whole, but we saw a particularly positive trend as we moved through the period, " said Glenn Tilton, UAL's chairman, president and chief executive officer.

BBC: United Airlines trims losses

But if no agreement can be reached on how to enact such plans, the euro zone will face a "severe and fundamental challenge, " he added.

WSJ: Tony Blair: Euro is at a 'Final Decision Point'

Unions described their comments as "ridiculous" and said the most serious challenge facing the economy was a "severe lack of jobs".

BBC: British workers 'among worst idlers', suggest Tory MPs