Much maligned for their history of disappointing not only customers but also employees and shareholders, airlines have nevertheless enjoyed a banner quarter. Two of the largest -- Delta Air Lines (NYSE:DAL) and United Continental (NYSE:UAL) -- have enjoyed some of the best returns over that period, up 36% and 23%, respectively.

Both carriers are expected to announce lower profits when reporting Q4 results this week. Not surprising, really, when you consider that oil prices are up about 5% over the quarter. Yet some other carriers are thriving: US Airways (UNKNOWN:LCC.DL) expects to report a 46% jump in profit this week.

If the airlines are to continue to rally, it'll take more than a slim earnings beat, says Motley Fool Rule Breakers and Motley Fool Supernova contributor Tim Beyers. Click the video below to hear about the one statistic he believes matters most to airline investors. And where you're done, please leave a comment to let us know what you think about the major carriers and their peers, and whether you'd invest in any of them at current prices.

Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team and the Motley Fool Supernova Odyssey I mission. He didn't own shares in any of the companies mentioned in this article at the time of publication. Check out Tim's Web home and portfolio holdings, or connect with him on Google+Tumblr, or Twitter, where he goes by @milehighfool. You can also get his insights delivered directly to your RSS reader.

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