Frank Borman, a NASA astronaut who commanded Apollo 8, the first crewed mission to orbit the moon and return safely to Earth, and later as chief executive of Eastern Air Lines piloted the carrier through a turbulent business climate that led to its takeover and eventual demise, died Nov. 7 at a medical center in Billings, Mont. He was 95.

The cause was a stroke, said family spokesman Jim McCarthy. Mr. Borman, who lived at a retirement community in Billings, died one week after fellow astronaut Ken Mattingly, who helped bring Apollo 13 home following an onboard explosion.

Mr. Borman became America’s oldest living former astronaut after the 2016 death of John Glenn, one of the seven original astronauts in NASA’s Mercury program.

After graduating near the top of his U.S. Military Academy class, Mr. Borman became an Air Force test pilot of supersonic jet fighters. He once refused to eject from an F-104 fighter whose engine failed at twice the speed of sound, instead managing to steady the plane until it recovered power. He won an award for flight safety.

“With delicious irony,” he wrote in his 1988 memoir, “Countdown,” “they also gave the award to another pilot for not restarting his engine under almost the same circumstances. He had bailed out instead, and the investigators found that if he had restarted his engine, he would have blown the plane into five million pieces.”

In 1962, Mr. Borman was one of nine men tapped for NASA’s second astronaut corps and served as command pilot of two NASA missions that laid essential groundwork for the 1969 moon landing.

During the December 1965 flight of Gemini 7, he and astronaut James A. Lovell Jr. set an endurance record in space. They spent two uncomfortable weeks orbiting the Earth in what Mr. Borman later described as a capsule the size of “the front seat of a Volkswagen.”

Under nonstop medical monitoring, the men put up with boredom, heat and unsanitary conditions, even sharing a toothbrush for part of the mission. Lovell joked afterward that he and Mr. Borman had decided to get engaged.

In space, Gemini 7 got within six feet of the crewed Gemini 6, proving that NASA could perform the rendezvous maneuvers needed in lunar missions. Until Mr. Borman’s and Lovell’s orbiting medical experiment, space historian Andrew Chaikin said in an interview, NASA wasn’t sure that humans could survive such a long trip in space.

Mr. Borman and Lovell were rewarded with leadership roles on Apollo 8. The mission had been planned to orbit Earth, but intelligence reports that the Soviets were readying a crewed mission around the moon led NASA to change its plan, sending Mr. Borman, Lovell and crewmate William Anders more than 230,000 miles away from Earth and to orbit the moon 10 times.

It was a bold gamble for the space agency and for the three astronauts, who became the first humans to leave Earth’s gravitational field and the first to orbit the moon. Anders snapped an iconic photograph, known as “Earthrise,” showing the planet’s dawn above the lunar horizon.

Mr. Borman coordinated the Apollo 8 crew’s live Christmas Eve message, during which the three astronauts read from the first 10 verses of Genesis, their television camera trained through the capsule’s window, toward the moon.

“And from the crew of Apollo 8 we close with good night, good luck, a Merry Christmas and God bless all of you – all of you on the good Earth,” he said in the broadcast’s final moments.

“Earth looked so lonely in the universe. It’s the only thing with color,” he said years later, of that Christmas Eve. “All of our emotions were focused back there with our families as well. So that was the most emotional part of the flight for me.”

Within the space agency, Mr. Borman was known for an unyielding commitment to protocol. When director of flight crew operations Deke Slayton sent small bottles of contraband brandy on Apollo 8 for the astronauts to enjoy as a Christmas treat, Mr. Borman refused to let anyone partake.

“You know, I didn’t think that was funny at all,” Mr. Borman told a NASA oral historian in 1991. “If we’d have drunk one drop of that damn brandy and the thing would have blown up on the way home, they’d have blamed the brandy on it. You know, I wanted to do the mission and I didn’t care about the other crap. I didn’t care about the food or anything else. I just wanted to get it done.”

After Apollo 8, Mr. Borman joined NASA administration as deputy director of flight crew operations. He retired from the military and the space agency in 1970. He later cited family stress as a major reason for leaving the astronaut corps, in particular his wife’s alcohol dependency.

Each spouse, he wrote in “Countdown,” “was expected to appear to the public as the Perfect Wife married to the Perfect Husband who was a Perfect Astronaut in a Perfect American Family raising Perfect Children. But how they were supposed to accomplish this was totally ignored.”

According to one account, at the moment on Christmas Eve when Apollo 8 was about to circle the moon and lose its signal to Earth, Susan Borman asked mission control to pass along a coded message to her husband: “The custard is in the oven at 350.” It was a long-running inside joke, her way of assuring Mr. Borman that she was okay, and that everything at home – “the custard” – was under control.

“No comprendo,” he replied to mission control, engrossed in his duties. It took him some time to realize what she had been saying.

“Why did she never say anything to me?” Mr. Borman later asked, referring to his wife’s anxiety during that period, in his memoir. “Because at that stage of our lives, it wouldn’t have done a damned bit of good. This was Frank Borman she was married to, a man determined to complete whatever the Mission happened to be. I would have been upset if she had confided what was eating away at her.”

After leaving NASA, Mr. Borman became vice president at Eastern and, in 1976, was named chief executive.

He found the storied carrier, once led by the World War I flying ace Eddie Rickenbacker, close to bankruptcy. He returned it to profitability, implementing cost cuts and even appearing in commercials. He won plaudits for some aspects of his management style, even working the baggage carousels during the holiday season.

“The Colonel,” as Eastern employees called him for his Air Force rank, banned alcohol at events for corporate executives and did away with other perks for senior managers. He drove a battered 1969 Chevy convertible to work, setting an example of thriftiness.

His successes were short-lived. When the U.S. government began deregulating the nation’s airlines in 1978, Eastern wasn’t equipped to ride out the instability, industry analyst Richard Aboulafia said in an interview for this obituary. The company had built its business model during an era of government-set fares and markets. As ticket prices fell and revenue decreased, Eastern had trouble cutting costs. Further, Mr. Borman became mired in protracted, hostile salary negotiations, and employee morale slumped.

He resigned in 1986, after Eastern – the country’s third-largest carrier – was acquired by low-cost Texas Air for $676 million. (The airline continued to struggle, selling its shuttle business to future president Donald Trump in 1989. Eastern shut down operations in 1991. USAir acquired the Trump Shuttle the next year.)

Aboulafia said Mr. Borman was a “remarkably accomplished fighter pilot at the dawn of the jet age, a remarkably accomplished astronaut, and then a respected airline executive – but he was in the wrong place at the wrong moment.”

In his memoir, Mr. Borman recalled driving home and crying on his wife’s shoulder when Eastern’s board sold the airline. “For the first time in my life, I hadn’t accomplished a mission,” he wrote.

Frank Frederick Borman II was born in Gary, Ind., on March 14, 1928. He suffered from breathing trouble, and the Bormans relocated to Tucson in the hope that the dry desert air would improve the health of their only child.

He would later recall “a halcyon existence,” capturing Gila monsters and walking downtown to watch movie westerns on Saturdays. He excelled in school, became quarterback of the Tucson High School football team and met Susan Bugbee, his future wife, during his senior year.

Mr. Borman built model planes in childhood and, as a teenager, worked odd jobs to earn money for flight lessons.

In 1950, the year he married, he graduated eighth in his class at the U.S. Military Academy at West Point, N.Y. He received a master’s degree in aeronautical engineering from the California Institute of Technology in 1957.

His wife died in 2021. Survivors include two sons, Frederick and Edwin Borman; four grandchildren; and six great-grandchildren.

The “last thing I ever wanted to be was a professional astronaut,” Mr. Borman told the NASA oral historian. Invoking the baseball Hall of Fame pitcher, he added: “I just try never to look back. Like Satchel Paige said: Somebody might be gaining on you if you look back.”