With more than 100,000 frequent flier miles, Jan Philpot is one of US Airways' repeat first-class travelers.

That means her checked luggage is labeled "priority" and is supposed to be among the first pieces unloaded.

But on five flights since April, Philpot's bags did not arrive with her at her destination. Instead, US Airways had to arrange delivery of her bags the next day.

The most recent baggage bungling occurred on Oct. 29, when Philpot, an executive at Carnegie Mellon University's Software Engineering Institute in Ballston, arrived at Reagan National Airport from Monterey, Calif. Her bags failed to make the connection through Philadelphia and arrived seven hours late. Philpot said a baggage employee at National told her that the handlers were short-staffed, and those who were still working were angry because of a 21 percent pay cut recently imposed by a bankruptcy court.

"In the future, I'd rather fly coach nonstop on another airline than remain loyal to US Airways -- unless I can carry what I need on board," Philpot said.

Savvy frequent fliers often travel light: a carry-on overnight bag at most. But in some cases, checking bags is unavoidable -- and passengers must put themselves at the mercy of airlines' baggage handling operations.

US Airways' baggage problems extend beyond Philpot. Travelers in Philadelphia waited nearly two hours Sunday for their bags after an unusually high number of employees called in sick, said US Airways spokeswoman Amy Kudwa. The airline's baggage handlers also had to grapple with a faulty mechanical system that required them to load bags manually for most of the day.

Last month, some Philadelphia baggage workers failed to show up for work, forcing some travelers to wait nearly 90 minutes for their bags to arrive on the carousel.

Philadelphia is one of US Airways' largest hub airports and thousands of travelers and bags are directed through the airport each day.

Joe Tiberi, a spokesman for the International Association of Machinists, the union that represents the airline's baggage handlers, said the Philadelphia workers were not participating in a "sick-out demonstration" on Sunday. He claims the operation was sharply understaffed. US Airways executives said staffing was adequate.

Reports of mishandled baggage at US Airways soared to 11,902 in September, up 51 percent over September 2003, according to the latest statistics from the Department of Transportation. The airline had an increase of 6 percent in total passengers during the month.

On a per-thousand-passenger basis, however, other airlines had worse records of complaints about baggage than US Airways during the month. Atlantic Southeast Airlines had the highest level, 11.03 per 1,000 passengers, followed by Delta Air Lines' connecting operation, ComAir, at 7.79. US Airways' figure was 4.05 per 1,000.

But US Airways had the highest number of overall complaints made directly to the Transportation Department (1.38 per 100,000 passengers) among the top 19 U.S. airlines in September. The airline's total complaints about such issues as customer service, refunds and canceled and delayed flights increased 55 percent from the same period a year ago.

While travelers are enjoying some of the lowest air fares in more than a decade, they are also complaining more. Between January and September, the Transportation Department received 4,296 complaints, a 16 percent increase from the same period a year ago.

America West Airlines had the largest number of complaints per 100,000 passengers for the first nine months of the year. US Airways was fourth, according to the Transportation Department.

Most complaints never make it into the department's statistics because travelers most often take their problems directly to the airlines.

US Airways spokesman David Castelveter said September was a difficult month for the Arlington-based airline because of its bankruptcy and the hurricanes in Florida -- one of the carrier's most popular destinations.

Castelveter said the airline was flooded with calls from angry customers who wanted refunds because of the storms and from others who feared the airline was going out of business and requested refunds without a financial penalty.