US Airways, once the dominant carrier at Pittsburgh International Airport, flew its final flight on Friday. The last plane flying under the US Airways name took off from San Francisco and landed in Philadelphia.

The flight number — 1939 — was chosen for the year that a small airline company called All-American Aviation was born and later grew to become US Airways. In 2013, US Airways was merged with American Airlines.

Former US Airways employees around the country celebrated the flight to Philadelphia. They recalled the days when the airline dominated the Western Pennsylvania market and was a profitable national carrier.

While 500 former US Airways employees gathered at Pittsburgh’s airport for a “Final Flight Party” on Friday evening, the mood was bittersweet. According to Pittsburgh newspaper accounts of the event, former pilots, flight attendants and support workers talked about the good times but also the painful job losses.

Resentment lingers over the airline’s downgrading of the Pittsburgh airport’s hub status. The airline scaled back Pittsburgh flights and operations to concentrate its eastern hub operations in Philadelphia and Charlotte, N.C., despite earlier promises to grow Pittsburgh’s operations.

There was a time when US Airways offered 700 flights a day from Pittsburgh to more than 100 destinations. Today, those figures have fallen to just 173 daily flights to 51 cities.

The airline was once a major regional employer with more than 10,000 workers. The decline of US Airways in Pittsburgh meant inconvenience for travelers, but more than that it meant the loss of thousands of well-paying jobs.

Beyond the pain of lost jobs is the fact that the Pittsburgh International Airport was built largely to accommodate US Airways and its plans for growth. The airport authority borrowed more than $900 million to build the $1 billion facility to suit US Airways’ needs and hub expansion plans. The airport, praised as state-of-the-art when it opened in 1992, is now underused, with some gate areas having the feeling of a ghost town compared to other, busier airports.

The loss of so many US Airways flights has also meant reduced landing and gate-fee revenue for the airport authority, which still has $230 million in debt tied to the airport’s construction. The annual payments today are $65 million, but will drop to $20 million a year by 2019 and decline further to $5 million by 2020. There is hope that lower debt payments will be coupled with lower landing and gate fees, which could bring more flights.

After decades of struggling finances and several bankruptcies, the big legacy airlines used mergers to reduce costs and compete with low-cost carriers. In the past 12 years, the airline industry has gone from 10 large companies to just four. Gone are TWA, America West, Northwest, Continental and AirTran. The four major carriers — United, Delta, Southwest and American — dominate the U.S. market.

The US Airways merger with American probably was inevitable after the other major carriers merged.

The loss of hub status hurt the Pittsburgh economy — and the airport’s debt payments and higher fees have made it less competitive. Reduced debt payments over the next several years could help the airport offer more flights. But fees are not the only consideration — airlines still need passengers to fill the planes. Recent airline profitability is mostly due to planes flying with very few empty seats. Lower jet fuel costs and more fuel-efficient planes have helped, but not flying half-empty planes is key to airline profitability.

Some of US Airways’ planes will keep the company logo on their exterior until they are scheduled for repainting, but in reality, US Airways has flown into the history books.