With 'terrorist' incidents breaking out everywhere from San Bernardino to the south of France, it is perhaps no surprise that the world's airlines are struggling. But, as Bloomberg notes, over-capacity, rising fuel costs (so far this year), and weaker demand have hurt profits and crushed airline stocks to their worst year since 2008...

Down over 18% this year...

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Troubles keep mounting for the world’s leading airlines. With the group already struggling with overcapacity and weakening global demand, Bloomberg reports that Lufthansa and EasyJet Thursday said terror threats could hurt profits, while Southwest Airlines predicted airfare cuts will accelerate.

The Bloomberg World Airlines Index tumbled 2.8 percent for a third straight loss. The group has posted the worst performance since 2008, dramatically lagging global stocks...

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Charts: Bloomberg