US transportation officials on Monday launched a probe into the holiday air travel mess at US Airways and Delta Air Lines' Comair unit that left thousands of passengers stranded and others without luggage.

US Transportation Secretary Norman Mineta said his department would investigate the disruptions, which the two airlines attributed to a combination of bad weather, computer malfunctions and unexpected staff shortages.

"It is important that the department and the traveling public understand what happened, why it happened and whether the carriers properly planned for the holiday travel period and responded appropriately to consumer needs in the aftermath," said Mineta.

Bankrupt US Airways was still experiencing some delays on Monday after an unexpectedly high number of employees called in sick over the Christmas weekend, forcing the cancellation of hundreds of flights and leaving about 10,000 bags separated from their owners.

Meanwhile, Delta's regional carrier Comair, grounded by a computer shutdown on Christmas Eve, said it hoped to run 60 percent of its 1,160 daily flights on Monday.

Mineta cast doubt on the airlines' excuse that weather was a primary factor for the problems, noting that no other big carrier reported weather-related problems over the weekend.

"We will of course cooperate with their inquiry although we believe the facts are relatively simple, and the efforts of the company and 99 percent of our employees have been to take care of our customers," said Amy Kudwa, a US Airways spokeswoman.

A Comair spokesman was not immediately available for comment.

At US Airways, the troubles threatened to further alienate customers as the carrier fights to avoid liquidation by cutting employee pay and other costs. The company suffered a net loss of USD$58.4 million in November.

FINANCIAL TIGHTROPE

"This airline cannot afford to have any reductions in revenue right now," said Michael Boyd, an airline industry analyst. "When your employees are this disaffected and the financial condition of the airline is this weak, it's really questionable whether they can get through this."

US Airways pilots, customer service workers and smaller unions have ratified wage concessions, while flight attendants have reached a tentative deal for givebacks.

Mechanics and baggage handlers continue to negotiate, but their union denied organized action against the airline.

In a recorded message on Sunday, US Airways Chief Executive Bruce Lakefield criticized employees who called in sick. "Let's not forget who pays our salaries -- our customers," he told the employee hotline. "This weekend did nothing to earn their confidence and future business."

US Airways said it canceled just 15 flights on Monday due to snow in New England. There were some delayed flights from Philadelphia because of baggage loading problems.

The airline said it had whittled its backlog of lost luggage to under 1,000 pieces, flying and trucking them to Charlotte and Pittsburgh to reunite them with their owners.

Meanwhile, Comair said it would try to resume its full schedule by Wednesday.

"Comair employees in every area of the organization continue working nonstop to resume full flight operations as safely and quickly as possible," Don Bornhorst, Comair's senior vice president of customers, said in a statement.

Much of the US airline industry is still walking a financial tightrope years after the September 11, 2001 attacks.

(Reuters)