Officials in charge of building the Silver Line could decide as soon as May 3 who will build the project's billion-dollar second phase between Reston and Washington Dulles International Airport.

The Metropolitan Washington Airports Authority will open bids from five companies on Friday in a public meeting, officials said Wednesday. The low bidder will win the contract -- estimated to be worth as much as $1.6 billion -- provided the math adds up and it meets other qualifications, officials said.

"At this point in time, the award will be to the lowest responsive and responsible bidder," said Silver Line project manager Pat Nowakowski on Wednesday.

As long as losing competitors don't legally challenge the results of the bidding, the winner would start work on the second phase of the Silver Line in July, officials said. When it's complete, Metro riders could take the Silver Line all the way to Dulles by 2018.

Airports leaders meeting Wednesday questioned whether choosing the lowest bidder was the wisest course, since a low bid could force the project to go over budget later.

"There's always a concern when we have a low-price procurement that someone will come in and buy the bid and then make up the difference through change orders," said board member Warner Session.

But Nowakowski said the five bidders already passed technical tests that will prevent unreasonably low bids and that the airports authority would carefully oversee the contract to prevent the winning firm from going over budget.

"We will hold them to their technical proposals to deliver that contract to us," Nowakowski said. "I think we're in a very good stage in terms of making very clear, concise contract terms that will not have to change."

About 20 union laborers who have been working on the project showed up to the airports authority Wednesday with a letter asking to be rehired for the second phase of the Silver Line.

"I want to be rehired because this is the best job in the mid-Atlantic area," said Jeffrey Bowers, who worked on the project for two years and said he was trying to help pay for his granddaughter's college tuition. "It pays very well. I'm able to support my family and live the lifestyle that I'm comfortable [with]."