WARWICK — The Rhode Island Airport Corporation yesterday promoted its top lawyer, Peter A. Frazier, to head the agency as it searches for a permanent replacement for Mark P. Brewer.

Brewer, the executive director since 2004, is leaving next month to run the Manchester-Boston Regional Airport, in New Hampshire. He earns $188,000 for overseeing T.F. Green Airport, the North Central airport and state airports in Quonset, Block Island, Newport and Westerly.

Frazier, the first staff attorney at the 15-year-old agency, will have to guide three costly and complex projects at Green until the corporation’s board appoints Brewer’s successor: an $83.5-million renovation of the terminal, a $242-million new airport transportation hub, and a controversial effort to expand the runway.

Kathleen C. Hittner, the agency’s chairwoman, says Frazier will succeed as temporary caretaker because he has been involved with those projects for several years.

“We don’t expect any slowdown in any of our projects. He is a very good leader,” Hittner, an anesthesiologist and the president of Miriam Hospital, said yesterday. “He really knows what’s going on, and he has a relationship with the board.”

The agency’s human resources committee — made up of Robert Sangster, Joseph M. Cianciolo and James C. Forte — endorsed Frazier as interim director Nov. 14. The full board unanimously approved the appointment yesterday.

“The board recognizes Peter’s involvement in a number of critical airport projects and feels he will serve the corporation well in the interim position,” Hittner said in a statement after the vote.

Frazier, 48, has worked for the agency for less than three years. He was hired in February 2005 as chief general counsel after leaving the Holland and Knight law firm.

But Frazier has worked extensively in the aviation industry, according to Patti Goldstein, the agency’s spokeswoman.

After completing a law degree from the University of Akron, in Ohio, Frazier earned a master’s degree in air and space law at McGill University, in Montreal. At Holland and Knight, he specialized in aviation law.

Frazier is not in the running to replace Brewer as the agency’s fourth director, Goldstein said. The board has hired The Mercer Group, of Atlanta, to lead a nationwide search for a successor.

Yesterday, the board appointed board members Hittner, Cianciolo and Russell W. Hahn to an internal search committee.

“This is a very pivotal time for us,” Hittner said. “We want to make sure we do this right.”

Frazier’s tenure as interim director, meanwhile, may be short. Hittner said the board has scheduled five interviews for next month, including candidates identified by The Mercer Group, and others who approached the agency independently.

Brewer’s replacement could be named by spring, she said.

“I don’t think it will be that long. It’s a pretty popular job,” Hittner said. “I don’t think we looked for a long-term, short-term solution.”

She declined to disclose the names of the candidates.

Frazier will become interim director Saturday, although Brewer does not plan to leave the airport corporation until Dec. 21. In that period, Brewer will perform “special transition assignments,” according to a resolution passed by the board yesterday.

The airport corporation recently named a replacement for Laurie Cullen, the former senior vice president for planning, engineering and environment. Ann Clarke is scheduled to start next week, almost two years after Cullen left.

The board is still searching for a successor to Marci Greenberger, the senior vice president of operations and maintenance. She left in August.

In addition to the expansion projects, Brewer’s replacement will inherit an airport at perennial loggerheads with its neighbors and grappling with steep declines in passenger traffic.

Last year, the number of people using Green plummeted by 9 percent, from 5.7 million in 2005, to 5.2 million last year. This year, airport officials have projected that passenger traffic will be about 5 million, a potential 4-percent drop.

But Hittner insisted that those trends would not discourage quality candidates. “It isn’t going to make it difficult,” she said. “We have people who are very interested in the challenge.”

bgedan@projo.com