American Airlines and Continental Airlines both provided discouraging revenue guidance

. AA in an investor update wrote, "First quarter mainline unit revenue is expected to decrease between 9.6 percent and 10.6 percent year over year." According to a Continental Securities and Exchange Commission filing, "largely as a result of declining business travel, the company has experienced year-over-year yield degradation, which has accelerated sequentially since January 2009 and has become significant."