The Washington region's three major airports have all seen surges in business in recent years, but any future growth is going to require local officials to maintain easy access to the airfields, a new analysis shows.

A survey of airline passengers conducted by the Metropolitan Washington Council of Governments showed that most people pick an airport based on how conveniently located it is. So access to the airports is crucial to their growth and, ultimately, to the growth of the local economy, experts said.

"If access to an airports is the main reason you want to go to a particular airport, improving access is really important," said Ron Kirby, director of transportation planning for the COG. "Those airports are going to influence location of business, and even their decision to come to the region."

The COG's data show that Washington Dulles International Airport now handles 36 percent of the region's air travelers. Baltimore/Washington International Thurgood Marshall Airport handles 35 percent of local passengers, and Ronald Reagan Washington National Airport gets 29 percent.

Federal Aviation Administration statistics show that Dulles could triple its business by 2040. BWI could double its take by then, and traffic at Reagan National could increase by a third.

"Essentially what we're saying is that growth in business and cargo is going to be important to the economy, and improving ground access to BWI and Dulles will be very important," Kirby said. "And that really keys back to what the passengers said is more important to them."

Experts said Dulles is expected to grow more thanks to the coming Silver Line, as well as its larger chunk of land, which will allow it to add a runway and another terminal in the future.

"Dulles has an enormous capacity to handle future growth," said airport spokesman Rob Yingling. "[And the Silver Line] will certainly be helpful to Dulles' future."

BWI spokesman Jonathan Dean said his airport won't be losing out in the region's future growth.

"As long as the region continues its projected growth, all three airports will be important for the region," he said.