Six years ago, the nation's airlines pledged to improve customer service to avoid threatened mandates from Congress.

They agreed to a passengers' bill of rights and promised, among other things, to notify customers of flight delays and cancellations, to show more responsiveness to passenger complaints and to meet essential needs during long on-aircraft delays.

Now a key member of Congress wants to see if airlines are living up to their pledges. Rep. John L. Mica (R-Fla.), chairman of the House transportation subcommittee on aviation, has asked the Transportation Department's inspector general for an analysis of the airlines' commitment to the passengers' bill of rights. The study will look at the progress of the airlines at a time when most are wrestling with mounting financial losses, smaller staffs and even bankruptcies.

Mica said he feared that many of the commitments may have been "swept under the table" by airlines struggling to regain their financial footing in the aftermath of the 2001 terrorist attacks. He plans to hold hearings on the issue in the fall.

Air travelers submitted 2,193 complaints to the Transportation Department in the first quarter, up 40 percent from the same period a year ago. The complaints targeted the same problems that existed when Congress first delved into the issue: lost bags, delayed and canceled flights and poor customer service.

Mica said he wants the latest analysis to give a broader portrait of airline services than has previously been available. For instance, he wants to know how much information carriers give travelers when flights are affected by security or safety problems.

Mica also wants to examine the fees that airlines demand when travelers change their flight plans. For example, passengers incur a charge of $50 to $100 to change a ticket, depending on the carrier. By contrast, if an airline reschedules a flight, passengers do not receive compensation.

"I think there needs to be a level playing field for both the airlines and the passengers," Mica said. "The airlines are less willing to deal equitably with the passenger. They're imposing lots of penalties on the passenger, but what about the consumer?"

David Barnes, a spokesman for the inspector general, said the department was considering the review. "We try to be responsive to our members of Congress," Barnes said.

The nation's airlines said they would go along with any requests for information. "We don't feel that a review is needed, but if the inspector general feels differently, then the carriers welcome a review," said Diana Cronan, a spokeswoman for the Air Transport Association.

Mica's request comes as the airlines are grappling with one of the busiest summers since the Sept. 11, 2001, terrorist attacks. They also are experiencing a growing number of delayed and canceled flights because of summer thunderstorms and the effects from the hurricanes.

The review of the pledge is the first since February 2001. At that time, Kenneth R. Mead, the Transportation Department's inspector general, wrote that the airlines had made some progress in certain areas such as providing the lowest fares available at the time of booking.

But, he said, the airlines needed to improve their response in relaying accurate and timely information about delays and cancellations. Mead found in his 14-month investigation that airlines frequently relayed misinformation about the causes and expected lengths of delays.

"As the skies get even more filled to capacity, it's important we have a good set of ground rules for the flying public and the airlines," Mica said.

US Airways' Web Site Guarantee: US Airways yesterday said it would award a $50 travel voucher to customers who find tickets for the same US Airways flights selling at least $10 cheaper on another Web site. Travelers must find the cheaper fare on the same day they book their US Airways flight. They then have to submit a claim to usairwayslowestpriceguarantee.com.

Other airlines such as American, Northwest and Continental offer similar guarantees.