American ( AMR) became the latest airline to report that first-quarter unit revenue will decline. First-quarter consolidated revenue per available seat mile is expected to decrease between 10.2% and 11.2%, the carrier said Wednesday in a filing with the Securities and Exchange Commission. Mainline RASM is expected to fall between 9.6% and 10.6%, while cargo and other revenue is expected to fall 5.6% to 6.6%. In general, airlines are seeing declines in business travel, resulting in declining yields during a historically slow period for air travel. In a report Thursday, Avondale Partners analyst Bob McAdoo said American expects RASM declines similar to what other legacy carriers are seeing. He said "declining jet fuel prices should offset some of the revenue weakness (but) hedges on 42% of its 1Q'09 consumption have somewhat limited this positive impact." McAdoo now forecasts a first-quarter loss for American of $1.70, compared with his previous estimate of a 30-cent profit. Analysts surveyed by Thomson Reuters forecast a loss of $1.23. McAdoo said he continues to believe that American shares are undervalued. At midday Thursday, airline shares were lower as oil prices rose. American shares were down 32 cents to $3.11. Delta ( DAL) was down 50 cents to $5.57.