Air travel's hopeful revival is starting to stall

In the last month or two, we’ve seen lots of optimism from the airlines about a healthy recovery from the industry’s worst downturn in history – grounded aircraft being brought back, suspended routes reopening – but now it appears that optimism may have been premature as the air travel outlook is starting to turn south again.

Early last week, United Airlines announced ambitious plans to add hundreds more flights to its August schedule, but now it is scaling back those plans slightly, as its expectation of a continued increase in passenger demand is no longer showing up in advance bookings.