John Palmer, who told television viewers the story of their nation and world during 40 on-air years with NBC News and whose best-remembered scoop concerned the aborted U.S. mission in 1980 to rescue American hostages in Iran, died Aug. 3 at George Washington University Hospital. He was 77.

The cause was pulmonary fibrosis, said a son-in-law, Lee Cowan, a correspondent and substitute anchor for the CBS News program “Sunday Morning.”

Millions of Americans heard the news of their times from Mr. Palmer, who reported from around the United States and the world for decades as a correspondent. Many of his bleary-eyed countrymen welcomed the start of each weekday with him from 1982 to 1989, when he was news anchor of the “Today” show.

Mr. Palmer, a self-described “kid from the East Tennessee mountains,” held reporting assignments in New York, Tel Aviv, Beirut and Paris. Throughout the 1970s, he covered Arab-Israeli conflicts, the Arab oil embargo, the war in Cyprus and the civil wars in Lebanon and Angola.

On April 24, 1980, six months into his job as White House correspondent, he learned before any other reporter about the Carter administration’s failed attempt to rescue 52 Americans taken hostage in Tehran. A mob of militants had seized them the previous November in retaliation for Western support for the recently deposed shah, and many of the hostages were tortured with mock executions.

John Palmer

The rescue operation was canceled after a helicopter crashed with a transport plane, killing eight American servicemen, and several other helicopters were damaged by flying debris.

Mr. Palmer received a tip about unusual activity at the White House late in the night of the planned raid, a Thursday. Virtually alone as midnight approached, he caught sight of an unusually high number of limousines and other vehicles in the driveway.

Mr. Palmer started to phone the homes of top national security personnel, including Zbigniew Brzezinski, and his calls went unanswered. Mr. Palmer assumed the officials were at the late-night meeting. When he finally was able to confirm the story, he agreed to a White House request that he wait to report the news until the family members of the dead could be informed.

Mr. Palmer went on the air at 12:57 a.m. Friday, 21 minutes before his nearest competitor. His reporting earned him the White House Correspondents’ Association’s Merriman Smith Memorial Award for reporting under deadline pressure. (The Iranian captors released the hostages on Jan. 20, 1981, the day of Ronald Reagan’s inauguration as president.)

In all, Mr. Palmer covered five presidents and in the course of his work went fishing with Jimmy Carter, to the movies with former actor Reagan and to the golf links with Bill Clinton.

He anchored the first hours of NBC’s coverage of the space shuttle Challenger disaster on Jan. 28, 1986. He also wrote and anchored a 1988 one-hour documentary for NBC News, “The Pension Cookie Jar,” that helped identify a new threat to Americans’ financial security: corporate seizure of assets in employee retirement funds.

Writing in The Washington Post, television critic Tom Shales called the show “a prime-time documentary in which substance wins out over style. It has something to say that is also something worth hearing. That’s what broadcast news is when it’s good, and when it’s news.”

John Spencer Palmer was born Sept. 10, 1935, in Kingsport, Tenn. His father became an executive vice president with Eastman Chemical Products, a division of the photographic equipment company Eastman Kodak.

The younger Palmer graduated from Northwestern University in 1958 and received a master’s degree in 1959 from Columbia University’s journalism school. After brief Army service, he began his broadcasting career in 1960 at WSB-TV in Atlanta. He joined NBC News in Chicago in 1963.

In 1982, he married Nancy Doyle, a production assistant with NBC’s “Nightly News” show. Besides his wife, of Washington, survivors include three daughters, Molly Cowan of Santa Monica, Calif., Carter Palmer of West Hollywood, Calif., and Hope Palmer of Washington; and a sister.

In 1989, in one of the upheavals that periodically afflict morning TV, NBC ousted Mr. Palmer from his news anchor perch on “Today” in favor of Deborah Norville. He moved to “NBC News at Sunrise,” then left to broadcast for other media outlets.

After the announcement in 1994 that he was rejoining NBC to be a Washington-based network correspondent, Mr. Palmer appeared in the newsroom. The applause, of the kind that often goes unheard until the day of departure, lasted for quite some time.

“It was a long, long, long ovation,” he said later, “and I found it was just a little difficult when I tried to speak.”

He retired from NBC in 2002. But not retiring entirely, he hosted shows on Retirement Living TV, a cable network. He also was a volunteer reader and director at Recording for the Blind & Dyslexic of Metropolitan Washington and vice president of the board of trustees at Hillwood Estate, Museum and Gardens, a historic residence in the District.

He was, the Post television columnist John Carmody once wrote, “one of the nice guys” in TV news.

CORRECTION: An earlier version of this story inaccurately reported the date when American hostages were released from Iran in 1981. It was Jan. 20, not Jan. 21.