Joseph Sanchez looks through binoculars in at Baltimore-Washington International Marshall Airport on June 22, 2017. BWI is the region’s most used airport in terms of passenger traffic. (Kate Patterson/for The Washington Post)

As a frequent flier, Laura Wolfe is routinely looking to find the best fare, and she almost always finds it 33 miles north of her Dupont Circle home at Baltimore-Washington International Marshall Airport.

Reagan National Airport is closer, but Wolfe said the lower fares at BWI make getting there a secondary concern.

“If I had the option, I would obviously fly out of DCA, but it’s sometimes double or triple the cost,” Wolfe said. “So if I am paying for it, I am going to fly out of BWI.”

The low fares and the addition of more nonstop flights and airport amenities in recent years have made BWI an attractive alternative to National and Dulles International — so much so that in 2016, BWI beat both airports on passenger traffic. It is now the region’s busiest hub, with a record 25.1 million travelers.

[BWI, Reagan National airports set records for passenger traffic]

At least a third of the passengers flying out of Baltimore are from the D.C. area, according to BWI officials, and the airport is investing resources to expand that share.

“We want people to be aware that BWI is a better alternative,” said Ricky D. Smith, the airport’s chief executive. He said far too many people “still think of National and Dulles as their hometown airport.”

Last year, Dulles had 21.8 million people flying in and out. National had 23.6 million.

BWI officials said they have been able to cut into their competitors’ base by proactively marketing the airport’s low fares and nonstop options to Washington-area residents. Last year, a marketing campaign put ads on Metro trains aimed at changing the perception that Baltimore is not as accessible as Dulles, officials said. The airport plans to renew that marketing effort this year.

From the U.S. Capitol, it takes about the same amount of time to get to BWI as it does to Dulles — 35 to 40 minutes.

Wolfe, who doesn’t own a car, says she has figured it out. The consumer advocate, who flies out of Baltimore at least six times a year, said she takes Metro to Greenbelt, where she boards a bus that runs hourly — 6 a.m. to 9 p.m., Monday to Friday — to BWI. To avoid Metro’s track work, she sometimes goes to Union Station and hops aboard a MARC train. It’s just over an hour, on a good day, about the same time it takes to get to Dulles, she said.

It’s worth the hustle, Wolfe said.

“They have obviously been making huge efforts to update the airport and add new amenities,” she said. “Everything is nicer and snazzier than it once was.”

In recent years, the state-run hub has invested more than $500 million in capital improvements, including new gates, updated terminals and major airfield work. The airport has focused on growing its international program and bringing in new carriers for low-budget transatlantic flights.

Its dining and retail options also have gotten a facelift. And the airport has made itself a testing ground for innovative ideas. An app-based food-delivery program serves the airport, and a private gym has opened a fitness center there.

The improvements are similar to those happening at airports across the United States. At National, construction is set to begin this fall on a billion-dollar revamp that will add a new concourse, new security screening areas, road improvements and a new parking garage. In New York, LaGuardia is undergoing a multibillion-dollar redevelopment that officials say will transform the airport into a “world-class” hub. And a $1.6 billion midfield passenger terminal is being built at Los Angeles International Airport.

Many airports also are adding a wider variety of food options and — like BWI — turning to local businesses to bring in the flavor of the region. Maryland crab cakes are available in the airport at regional favorites such as Baltimore-based Phillips Seafood and Obrycki’s. Small, locally owned companies also are finding a home at BWI.

“We are getting our feet wet and our name out there,” said Newnew Norton, who runs the New Secrets Tea kiosk in the food court between Concourses A and B and also sells natural and medicinal products she makes in Baltimore. “There is a lot of foot traffic. That means there are many more noes before you get a yes.”

But despite the noes, Norton said the foot traffic has meant more business for her — and more revenue for the airport. In fiscal 2016, the airport’s revenue increased by $9.4 million, with more money coming in not just from parking and rental cars but also from concessions, rent and increased flight activity.

Experts say the gains at BWI and other major airports are, in part, the results of the strong economy and low fuel prices. Baltimore’s strategy to build on that growth is to keep the cost to airlines lower than at Dulles and National. The cost of enplanement — or boarding a plane — per person last year was $9.51. At Dulles, it was more than twice that amount — $20.95. It was $13.44 at National.

Because the airport has a single terminal, it avoids the costs associated with maintaining separate buildings, airport officials said.

But chiefly, the airport hasn’t spent as much as its counterparts on capital investments, which drive a large part of airport costs.

The Metropolitan Washington Airports Authority recently completed a $5 billion capital improvement program at Dulles that included the construction of an additional traffic-control tower, a fourth runway, a new midfield concourse and parking garages.

Dulles’s international travel is also more than four times larger than BWI’s, which likewise drives up costs. The Virginia airport serves 54 international destinations, compared with BWI’s 12. And aircraft for international flights typically spend more time at the gates, moving fewer passengers through a facility per hour, experts say. Fewer passengers per hour means higher cost per passenger.

[ BWI set to begin $60 million expansion of its international terminal ]

BWI is growing its international flight business, however, with plans to expand to more cities in Canada, the Caribbean and Europe.

Flights to Asia are planned within two years. In preparation, the airport is undergoing a $60 million expansion of its international terminal that will add six airline gates next year. The three-level, 70,000-square-foot extension to Concourse E will support international traffic, which grew by 1.2 million passengers last year, more than double 2010’s figure.

Already, British Airways has upgraded its service between Baltimore and London with last summer’s addition of a larger 787-8 Dreamliner aircraft to its daily service. Norwegian Air began service to the French Caribbean in December 2015. And the low-fare international airline Wow Air added flights between BWI and Reykjavik, Iceland, two years ago.

That investment followed a $125 million project completed last fall to connect Concourses D and E, the addition of a new security checkpoint, two new gates for international carriers, new food and retail concessions, as well as a new children’s play area, an outdoor patio space with airfield views and a gallery featuring regional artists’ work.

Domestic service also has grown. In the past year, the airport added flights to Portland, Ore., Seattle and Sacramento. At least five new low-budget carriers have opened shop at BWI in recent years, including Spirit Airlines, which began service in 2012 with nonstop flights to Fort Lauderdale, Fla., and Dallas. And the airline recently announced it will fly between BWI and Cancun, Mexico, starting in November. It now provides service to 19 markets from Baltimore.

Southwest Airlines, the airport’s top carrier, has seven international destinations from BWI, including service to Mexico, Costa Rica and the Dominican Republic — all added since 2015. About 70 percent of the flights from BWI are on Southwest.

BWI officials say they are encouraged by the positive trends and that they see no signs of a slowdown. And they want to keep it that way.

[BWI’s new gym doesn’t just provide space to exercise, but clothes, shoes and a shower]

Samuel Engel, an aviation expert based in Fairfax, Va., said BWI’s history of offering lower fares has put the airport into play for a large portion of Washingtonians.

“The question is, would somebody who lives in Arlington be willing to drive to Baltimore?” Engel said. “Clearly, that person will have a bias toward National or Dulles, but to the extent that BWI offers a better value proposition, it will be in the consideration set for that customer.”