AMR shares led a rally in airline stocks, rising 18 cents, or 7.1 percent, to $2.71 in trading.
Although investors were encouraged, employees at American had new reasons to worry about their jobs.
"These capacity adjustments could have a significant impact on operations and, unfortunately, could result in employee reductions companywide," said spokesman Tim Smith.
Smith said American was studying whether it could limit the number of furloughs by offering voluntary severance.
American said advance bookings are about in line with last year's, but analysts predict that travel demand probably will weaken in the fourth quarter.
Airlines usually cut capacity by reducing flights or using smaller aircraft. Both result in fewer seats for sale. That should help maintain airfares, a "positive for the airline sector," said Dahlman Rose & Co. analyst Helane Becker.
Even with the fourth-quarter moves, American's capacity for all of 2011 will still be 0.4 percent higher than 2010. But the increase is far smaller than the airline's original plan to grow by 3.5 percent.
American also plans to retire up to 11 Boeing 757 jets next year. It already has fewer pilots to fly its fleet of about 600 planes.
In the past two months, 240 American pilots have retired about 10 times the normal rate. They are taking advantage of an unusual contract clause that lets them lock in the value of some pension benefits before the recent stock market slump.
American parent AMR Corp. was the only major U.S. airline to lose money last year and is expected to keep posting losses through next year. High fuel prices have hurt American, which has a relatively old and inefficient fleet, and the company says that its labor costs are higher than those of competitors.