Is there no end to the red ink in the airline industry? The CEO of once-healthy Delta Airlines Inc. ( DAL ) says its balance sheet is "severely damaged to the point of exhaustion," while US Airways Group Inc. ( UAIR ) is struggling to comply with the terms of a $900 million federal loan guarantee. Other carriers are gasping as well. A huge part of the problem is that the big carriers still haven't fully faced up to their core dilemma. Even if they cut labor costs, they simply can't charge enough for their far-flung route networks to be competitive with the new breed of carriers such as Southwest Airlines Co. and JetBlue Airways Corp. ( JBLU ) that keep costs low with point-to-point service. The older carriers offer frequent service to many cities with short layovers. They do so by serving dozens of "spoke" cities through a handful of hub airports.