UPDATE 1-American Air Sept. revenue up despite flight problems

* Canceled flights held back growth

* Domestic traffic down, international rises

(Adds other performance measures)

Oct 8 (Reuters) - American Airlines on Monday said unitrevenue, a widely watched measure of pricing power, rose 4percent last month and would have been higher if not for flightdelays and cancellations connected with operational disruptions.

Though the number of passengers boarded fell 3.9 percentlast month on American and its regional carrier affiliates,passenger revenue per available seat mile, or unit revenue, rose4 percent in September from a year earlier.

The unit of AMR Corp , which filed for Chapter 11protection last November, said without challenges from thehalted flights in the second half of the month, the improvementin unit revenue would have been 0.4 point higher.

In recent weeks, American canceled hundreds of flights,citing increased pilot maintenance reports and sick leave usage.The Allied Pilots Association union, with which American iscurrently negotiating a labor contract, has said it has calledno work action at the carrier.

American Airlines said its unit revenue has outperformedother major U.S. airlines for the past six months as itrestructures in bankruptcy. For example, Delta Air Lines Inc

said its unit revenue rose 0.5 percent in September,while Southwest Airlines Co estimated a fall of 2percent to 3 percent in that measure for the month. US AirwaysGroup Inc reported flat unit revenue for last month.

Traffic at American Airlines, measured by revenue passengermiles, fell 2.8 percent in September on a consolidated basis.Domestic traffic fell 7.1 percent while international trafficrose 3.2 percent.

The airline's capacity, as measured by available seat miles,was down 3.4 percent. Load factor, or the percentage of seatsfilled, rose to 81.1 percent last month from 80.7 percent a yearearlier.

(Reporting by Karen Jacobs; Editing by Gerald E. McCormick)