Major Ferebee released the bomb, known as Little Boy, and 43 seconds later, at 1,890 feet above ground zero, it exploded in a nuclear inferno, leaving tens of thousands dead or dying and turning Hiroshima into scorched devastation.

Colonel Tibbets executed a diving turn to avoid the blast effects, but the Enola Gay was buffeted by a pair of shock waves. A flash of light that Mr. Van Kirk likened to a photographer’s flashbulb engulfed the cabin.

Photo

 

“The plane jumped and made a sound like sheet metal snapping,” Mr. Van Kirk told The New York Times on the 50th anniversary of the Hiroshima raid. “Shortly after the second wave, we turned to where we could look out and see the cloud, where the city of Hiroshima had been.”

He added: “The entire city was covered with smoke and dust and dirt. I describe it looking like a pot of black, boiling tar. You could see some fires burning on the edge of the city.”

Mr. Van Kirk remembered “a sense of relief.”

“Even though you were still up there in the air and no one else in the world knew what had happened, you just sort of had a sense that the war was over, or would be soon,” he told Bob Greene in Mr. Greene’s 2000 book, “Duty.”

Shortly before 3 p.m., the crewmen returned to Tinian and were greeted, as Mr. Van Kirk told it, by “more generals and admirals than I had ever seen in one place in my life.”

Three days later, another B-29 dropped a plutonium bomb on Nagasaki. On Aug. 15, Japan surrendered, bringing World War II to an end.

Theodore Van Kirk — everybody called him Dutch — was born and reared in Northumberland, Pa. He attended Susquehanna College for a year, then became an Army Air Forces cadet in October 1941.

Colonel Tibbets, flying with the Eighth Air Force out of England, selected Captain Van Kirk and Major Ferebee for his crew the next year. Their B-17 Flying Fortress, named Red Gremlin, became the lead plane in the 97th Bomb Group’s missions and flew Gen. Dwight D. Eisenhower to Gibraltar in November 1942 in preparation for the invasion of North Africa.

Photo

 

After 58 missions over Europe and North Africa, Captain Van Kirk returned to the United States to train navigators. When Colonel Tibbets was selected to command the 509th Composite Group, a unit of 1,800 airmen assembled in Utah in the fall of 1944 to train for delivering the atomic bomb, he brought Captain Van Kirk and Major Ferebee with him. This time they trained on the newly developed B-29s.

As Mr. Van Kirk recalled Colonel Tibbets’s words in a 2005 Time magazine interview: “He told me, ‘We’re going to do something that I can’t tell you about right now, but if it works, it will end or significantly shorten the war.’ And I thought, ‘Oh, yeah, buddy, I’ve heard that before.’ ”

In the summer of 1945, the 509th conducted its final training on Tinian, and President Harry S. Truman gave the order to drop the atomic bomb.

Mr. Van Kirk retired from military service in 1946 as a major, having received the Silver Star and Distinguished Flying Cross. He earned bachelor’s and master’s degrees in chemical engineering from Bucknell University and became a marketing executive with DuPont.

Besides his son Thomas, survivors include another son, Larry; two daughters, Vicki Triplett and Joanne Gotelli; seven grandchildren; and two great-grandchildren.

The crews that dropped the atomic bombs on Hiroshima and Nagasaki were seen by Americans as saviors for ending the war. But over the years, the morality of atomic warfare and the need for the bombings has been questioned.

Mr. Van Kirk joined his fellow crewmen in unwavering defense of the atomic raids.

“We were fighting an enemy that had a reputation for never surrendering, never accepting defeat,” he said. “It’s really hard to talk about morality and war in the same sentence.”

He continued: “Where was the morality in the bombing of Coventry, or the bombing of Dresden, or the Bataan Death March, or the Rape of Nanking, or the bombing of Pearl Harbor? I believe that when you’re in a war, a nation must have the courage to do what it must to win the war with a minimum loss of lives.”