The industry has yet to recover from an across-the-board revenue drop that followed the 2001 terrorist attacks. If thrifty consumers and cost-cutting businesses are this recession's legacies, airlines will be forced to shrink even more.

Growing smaller means parking planes, laying off workers and dropping destinations, meaning potential customers have fewer reasons to book. Earlier this month, Delta Air Lines Inc. cited a gloomy revenue outlook for the rest of the year in its plans to cut more management jobs. If passengers don't return to the skies and fares don't rise, some airlines could run low on cash, raising the specter of additional bankruptcies.

Airlines are suffering huge revenue declines as customers put off purchases, trade down to cheaper fares and bank more personal income. Airlines fear that this behavior will stick, exacerbating the "new normal" the industry has been grappling with for the past eight years.

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