"We're the third-largest region in the country in terms of airport travel, so it's good if we're all rising," he said. "It doesn't help if we take passengers from another airport or another airport takes passengers from us."
Kimberly Gibbs, a spokeswoman for the Metropolitan Washington Airports Authority, which operates Dulles International and Reagan National Airport, said it's "too early to speculate" on the implications of the increased MARC service on airport traffic, but that service is welcomed.
"Anything that increases access, transportation access, to the region, to our airports, we view as a good thing," Gibbs said.
All told, O'Malley announced $1.5 billion in transportation projects Wednesday, paid for with funding from a gas tax increase passed this year and including Baltimore's Red Line light rail and improvements on roads and highways near BWI.
Wiedefeld said transportation projects that increase connectivity in the region are welcome.
"Our motto is the 'easy come, easy go airport,'" Wiedefeld said, "so anything helps, whether it's transit or highway connectivity."
That is especially true, he said, as the airport weathers the federal budget cuts known as the sequester, which have diminished business travel among federal employers and contractors and personal travel among federal employees facing furloughs.
Transportation advocates also cheered the expanded MARC service.
Ragina Averella, a spokeswoman for AAA Mid-Atlantic, said in a statement that the expansion "is a positive step in providing affordable transportation options and a beneficial service for those wishing to travel from Baltimore to Washington on weekends, as well as to the airport."
Michele Whelley, president and CEO of the Central Maryland Transportation Alliance, which fought for the expansion, said it "will benefit every community between Baltimore and Washington, and will support job growth, residential communities, the entertainment industry, access to services, etc."
Weekend MARC train service begins Dec. 7:
Nine round trips between Penn Station and Union Station:
Penn Station departures: 7:35 a.m. to 9:15 p.m.
Union Station departures: 9:02 a.m. to 10:35 p.m.
Six round trips between Penn Station and Union Station:
Penn Station departures: 9:15 a.m. to 5:30 p.m.
Union Station departures: 10:40 a.m. to 7:00 p.m.
Two daily round trips between Penn and Union stations will be added, one likely this fall and another in the spring.