SUWON, South Korea — South Korea, an industrial and tech powerhouse, was once so poor that its citizens donated money so the government could buy five American fighter jets in case of a North Korean invasion.

Now, South Korea is a global weapons producer and seller. It is the third-largest arms supplier to NATO countries, with affordable weapons for nations seeking to refill their stockpiles of K2 battle tanks, K9 self-propelled howitzers and other items.

Its ascent underscores the nation’s dramatic economic and diplomatic evolution since that 1975 national fundraising drive for the American F-4 Phantoms.

South Korea retired those Cold War-era jets in June after more than five decades in use — making way for a new generation of homegrown fighter aircraft that will make South Korea one of the few nations to develop its own supersonic jet.

South Korea hopes its KF-21 Boramae will be a cheaper alternative to the U.S.-made F-35. The prototype was unveiled in 2021, and mass production is set to begin in 2026.

“South Korea is making a big push to engage globally,” said Peter Layton, a military analyst and visiting fellow at the Griffith Asia Institute in Brisbane, Australia. “They’re going from a big buyer to not just a maker but a designer of aircraft.”

Part of South Korea’s ambition is to be a bigger defense and security player, and that has led the nation to increase military and diplomatic coordination with the United States and its allies in the face of growing North Korean nuclear threats, China’s rise and Russian aggression.

South Korea is flying other American-made jets, including the F-5 and F-35 as well as jets developed jointly by the United States and South Korea.

Ahead of the F-4’s retirement, the South Korean air force gave me and five other journalists the rare opportunity of flying on a farewell trip.

The F-4 Phantom, a state-of-the-art fighter in the 1960s and the main U.S. aircraft used in the Vietnam War, was retired in the United States in 1996. South Korea operated 187 of the jets, and all of its F-4 versions ended service on June 6. The plane remains active only in Iran, Turkey and Greece.

For South Korea, the jet — which Koreans nicknamed the “Goblin of the Sky” — symbolizes the resilience of its alliance with the United States, forged in the aftermath of the 1950-53 Korean War, which ended in a cease-fire.

A peninsula transformed

In 1969, when the first six of these jets arrived, South Korea was being ruled by a military dictatorship and still emerging from wartime poverty.

At the time, North Korea, led by founder Kim Il Sung, was more affluent than the South and had a more powerful military. Washington knew that Seoul needed help beefing up its military inventory to defend itself against the North — including with the F-4 jets.

The arrival of the planes marked a turning point in South Koreans’ belief in their potential to shift the balance of air power between the two Koreas, air force officials say.

After purchasing five more jets through the 1975 national fundraising drive, South Korea declared its air power dominance over the North.

In the 1980s and 1990s, the jets were critical to South Korea’s air defense. They led counterespionage operations against North Korean spy ships, intercepted Russian reconnaissance aircraft and, in 1983, guided to safety a North Korean air force pilot who defected to the South on his Soviet-made MiG-19 fighter jet.

It wasn’t until I set foot in the F-4 that I felt the weight of South Korea’s transformation. In the air, I would gain a whole new perspective — literally and figuratively — on South Korea’s rise during the fighter’s lifetime.

Into the belly of the Goblin

The F-4 is a two-seater, with the pilot in front and another crew member in back. I climbed into the jet wearing more than 20 pounds of gear, and with clear instructions: Don’t touch anything you’re not supposed to.

I immediately noticed signs of the plane’s age — the worn-out belts and rusty switches and levers.

The jet rumbled as the pilot conducted safety checks. After a thumbs-up, our jets took off from Suwon Air Base, south of Seoul. The ride was smooth, but occasionally jerky as the pilot adjusted to stay in formation. It was nothing like a commercial flight, and felt almost like floating in a capsule.

The nearly two-hour flight gave me the rare chance to experience a remnant of history, while reflecting on South Korea’s economic transformation and the evolution of the U.S.-South Korean security alliance since the fighters first arrived.

We flew over Pyeongtaek, where Samsung Electronics is building the largest semiconductor plant in the world. In 2022, it was President Joe Biden’s first stop on his visit here, underscoring South Korea’s advancement in technologies that Washington views as critical to its economic competition with China.

I noticed the many golf courses along the way — in this status-obsessed country, golf is synonymous with wealth and luxury. The sport’s popularity grew along with disposable household income as South Korea’s economy rebounded after the 1997 Asian financial crisis.

The breathtaking route along the east coast brought us over the port cities that helped fuel the country’s export-driven growth, including Pohang, home to Posco, a South Korean steelmaker founded in 1968.

We ended the flight at Daegu Air Base, in the country’s south, where the F-4 was first introduced in 1969. I pressed the switch to open my canopy — one of the few buttons I was allowed to touch.

The flight brought home how dramatically the inter-Korean security dynamic has shifted.

Today, South Korea’s economy and military, bolstered by its alliance with the United States, vastly eclipse those of the North. Pyongyang is still depending on Soviet-era jets, while Seoul’s defense exports are booming globally. The Koreas are now playing a critical role in a global conflict: The North is supplying arms to Russia; the South is helping the United States and the West defend Ukraine.

The F-4 Phantom is leaving behind a Korea nothing like the one it came to more than five decades ago.