In a sweat, John W. Sutton dashed up to what he thought was the US Airways ticket counter yesterday at Washington's Reagan National Airport. A makeshift canvas sign behind the agent read: US Airways and America West.

The two carriers, which announced plans to merge in May, begin operating as a merged carrier today.

Sort of.

Sutton, who was flying US Airways to Atlanta, had actually shown up at the America West counter. But the agent there could not process him for a US Airways flight. So Sutton was sent down to the other end of the concourse to the US Airways ticket counter. He had only 30 minutes until his departure.

"This is really confusing right now," said Sutton, a Lexington Park consultant with BearingPoint.

Executives from the combined airline, which will be called US Airways, admit some kinks will occur as the carriers gradually put their operations together. They advised passengers to check in at the airline -- America West or US Airways -- that sold them their ticket. The two airlines will operate separately for about two years as the rebranding and merging of the operations slowly takes place. It will be several months before each airline will be able to process the other's passengers. Starting Oct. 5, passengers will have to earn more frequent flier miles to nab a free trip.

Frequent fliers will need 25,000 miles for a free trip on the combined airline, compared with 15,000 miles on America West and 20,000 miles on US Airways. Passengers will be able to earn and redeem miles on both carriers.

H. Travis Christ, vice president of sales and marketing for America West, who is overseeing the combined airline's frequent flier program, said raising the threshold will expand the number of free seats available on each flight.

Some US Airways frequent fliers said they weren't surprised by the increase, since 25,000 frequent flier miles was the minimum number of points required at several other carriers, including Northwest and Continental airlines. Alexandria economist Charles Witt said the increase was a "trade-off" for more destinations that would come from the merger.

The airline will also hand out fewer bonus miles for tickets purchased online. US Airways customers who purchase tickets on its Web site will now earn only 500 bonus miles, compared with 1,000 miles currently offered.

Also beginning on Oct. 5, travelers seeking to reach elite status will be able to start counting their trips on America West and US Airways toward that goal in 2006. The airline will no longer require passengers traveling on free awards to stay over a Saturday night.

Both airlines' frequent flier programs will remain separate through the spring. At that time, the new airline will eliminate America West's Flight Fund program while keeping US Airways' Dividend Miles frequent flier program.

Meanwhile, executives in Tempe, Ariz., where America West is based and the new US Airways will have its headquarters, were busy preparing for the change. The large green America West Airlines sign that has crowned its headquarters since the carrier's inception in 1983 was taken down and replaced by a big blue-lettered US Airways sign.

W. Douglas Parker, America West's president and chief executive, plans to be on the floor of the New York Stock Exchange today to mark the start of trading in the combined airline's stock under the symbol LCC. Parker will serve as the new US Airways president and chief executive.

Some America West frequent fliers said they are concerned that the merger would negatively affect their favorite airline's operations.

"America West has one of the better work cultures and I know US Airways has been struggling. I hope America West doesn't suffer for this," said Sira Maliphol of Arlington.

BWI Under a New Name: Baltimore-Washington International Airport will assume its new name on Saturday, becoming Baltimore-Washington International Thurgood Marshall Airport. New signs honoring the late Supreme Court associate justice and Baltimore native will begin going up around the airport today. The airport code, used for airline schedules, will continue to be BWI. The airport is also planning to erect a memorial to Marshall by the end of the first quarter.

Newly merged US Airways and America West begin dovetailing their operations today, their first day as one airline called US Airways.