American Airlines boosts outlook for key revenue measure

Unit revenue, also known as passenger revenue per available seat mile, is expected to grow between 5.5 percent and 6.5 percent in the second quarter from a year earlier, American said in a statement. That's up from its forecast in April of 4 percent to 6 percent growth in the three months through June.

Recent profit warnings from European airlines have raised concern about demand trends and pummeled share prices.

Last week, Delta Air Lines said unit revenue for June grew less than it had forecast, citing lower business demand to Latin America during the World Cup soccer tournament and capacity increases that hurt ticket prices.

(Reporting by Karen Jacobs in Atlanta; Editing by Bernadette Baum)