UAL Corp.'s United Airlines set a goal of delivering passengers' bags within 25 minutes of arrival as the world's second-largest carrier tries to improve service and avert a federal directive.

The move is a response to record flight delays and rising complaints from travelers. Complaints reached a seven-year high in July, centered mostly on flight cancellations or lost luggage, the U.S. Transportation Department said Tuesday.

"Some government and special interest groups are calling for a passenger bill of rights," UAL Chief Executive Officer Glenn Tilton said in a message to employees Wednesday. Instead, Chicago-based United should "take the lead in delivering the best possible service we can."

United joins other airlines in vowing to focus more on fliers' concerns as the Coalition for an Airline Passengers' Bill of Rights urges Congress to mandate service improvements. To cut delays, American Airlines is adding five to seven minutes more ground time for each flight at major airports.

Tilton told employees United was unveiling, on its Web site and across the airline, the baggage-delivery "standard we've been working toward internally for some time."

"While we may not be achieving this delivery time consistently, we are setting the standard to ensure our customers know they should be able to expect it from us," Tilton said.

Other shifts include changes in how United handles planes stuck on the ground, "to lessen long ground and taxi-in delays," Tilton said.

United recently updated its eight-year-old customer-service pledge, "focusing particular attention on travel disruptions," Tilton said. The airline will review its new customer-service commitment every six months, with the next update planned for December, he said.

United fell 90 cents to $46.95 at 4 p.m. New York time in Nasdaq Stock Market composite trading. The shares have gained 6.7 percent this year.