The man who has spent 43 years modernizing Reagan National Airport and expanding Dulles International Airport into a major hub for overseas travel announced his retirement yesterday. James A. Wilding, 65, said he will step down in April as president and chief executive of the Metropolitan Washington Airports Authority.

Wilding has held the job since the federal government relinquished the two airports to regional control in 1987, becoming one of the most respected airport leaders in the country. Hired out of Catholic University in 1959 as a federal engineer to work on building plans for Dulles, Wilding climbed the ranks, eventually overseeing both airports during a period when passenger counts nearly doubled.

Travelers in his own terminals do not recognize him. But airport watchers say Wilding's stature and behind-the-scenes work were key to persuading President Bush to reopen National three weeks after the Sept. 11, 2001, terrorist attacks. He also oversaw the rebuilding of National's terminal, a $2.6 billion construction program underway at Dulles, and the implementation of federal security regulations after the hijacking attacks.

"Under his leadership, we've moved from having among the worst air service in the nation for a region our size to among the best," said Leo J. Schefer, president of the Washington Airports Task Force, a pro-airport lobbying group. "Our airports have gone from being a national joke to being envied and among the best. There aren't many people in any walk of life who when they retire can leave that kind of legacy."

Wilding also is credited with building the airports into a prime economic engine for the region. Any airport executive must juggle the demands of the Federal Aviation Administration, Wall Street, airlines, politicians and passengers, but Wilding is the only one who has done so with the airports closest to the nation's capital. Few other airports count so many members of Congress, powerful business leaders and White House officials among their frequent fliers.

"There's nobody in the industry more highly regarded for competence, for intellect . . . [with] a personality that is liked as well as admired," said David Plavin, president of Airports Council International, a trade group. "That's an incredibly unusual combination."

Wilding's retirement has been anticipated for several years. Yet, he took many airport watchers by surprise yesterday when he announced it as a characteristically understated postscript to his monthly report to the authority's board. Chairman Norman "Chip" M. Glasgow Jr. said the board is still deciding how to replace him. Wilding's deputy, James E. Bennett, is considered the natural front-runner, but several people close to the authority said they expected a national search.

Wilding said he has contemplated retiring before but stayed on, in part because of the Sept. 11 attacks, when National was shut down, and both airports were relying on a faltering airline industry for much of their income.

"All of a sudden, things were very unstable, and I didn't want to leave under those circumstances," Wilding said. "I thought I could help by sticking around."

Wilding runs both airports from the top down, said sources close to the authority. Little happens that doesn't, at some point, go directly through him. He is not one for small talk, but his admirers say he has used a deft diplomatic touch to balance the sometimes competing interests of the federal government, airlines, politically appointed board members and residents who live with the airport's noise and traffic.

"Jim can weave his way through Republicans and Democrats, between residents and the airlines," said Rep. James P. Moran Jr. (D-Va.), whose constituents have complained of noise from National's airplanes. "He's very adept in the world of politics, but he's not political. He knew how to stroke people and how to push and pull them."

Wilding, who lives in Silver Spring with his wife, Marcella, said he is considering writing a book about the public service side of aviation. He said he also hopes to spend more time with his growing family. His fifth grandchild is due to arrive next week.

As president and chief executive of the Metropolitan Washington Airports Authority, James A. Wilding has seen air travel take off.