Traffic and revenue expected to fall
American Airlines said it expects traffic and revenues to fall by more than 15% in the third quarter.
Mainline capacity also fell 9.7% in September compared to August in line with falls in passenger numbers, the airline said.
The news has caused American's share price to fall after 11 consecutive days of gains.
Analysts said the airline's forecast was not far from previous estimates and that its share price had suffered as traders sell at the higher prices.
American's share price had risen 20% following the news that it had raised $2.9bn in new financing, Reuters reported.
Mainline passenger traffic is expected to fall 16.4% this month compared to the previous month, American said in security filings on Friday.
Costs are also predicted to rise slightly this month on August levels. Over the third quarter costs are estimated at 12.28 cents per available seat mile, above the full year level of 12.06 cents.
Unit revenues may fall as much as 15.5% in the third quarter, the airline said.
Fuel costs are expected to average $2.07 per gallon in the third quarter and $1.99 for the full year.
The airline is reported to have hedged 33% of its fuel in the third quarter and 36% for the full year.
American said it expects to end the third quarter with a cash balance of $3.7bn including $1.2bn in new financing announced last week.