According to experts, the "belly landing" -- touching down with landing gear retracted -- was an unprecedented event for the $100 million US-designed stealth fighter now in use or on order by more than a dozen countries.
"The jet did an emergency landing as the landing gear did not extend. This would mean the jet did the 'belly landing,'" said a South Korean military official, who would not confirm whether the aircraft suffered any damage in the incident.
Even if it did, it would demonstrate superb flying skills by the pilot, whom officials said walked away from the landing, according to a South Korean military official.
"The F-35 lands really fast. It's not an F-16, 18 or 111," said Peter Layton, a former Australian air force officer now at the Griffith Asia Institute, referring to older, less sophisticated military aircraft than the F-35.
"I'm very surprised the emergency gear down systems didn't work, or weren't used," he said.
Layton also expressed surprise that the South Korean pilot didn't eject, "but clearly they did the right thing," he said.
An investigation into the incident was underway, South Korean officials said.
South Korea received its first US-made F-35 in 2019 as part of an initial order of 40 of the single-engine jets, according to the plane's manufacturer, Lockheed Martin.
Versions of the F-35 are also flown by the US Air Force, Navy and Marine Corps as well as US allies and partners including Japan, the United Kingdom, Australia, Italy, Norway, the Netherlands and Israel. More countries have orders in for the jet.
Tuesday's accident is the first for a South Korean F-35, but the jets have been involved in at least eight other incidents, according to records kept by crowdsourced website F-16.net.
Lockheed Martin says the F-35 "is the most lethal, survivable and connected fighter aircraft in the world, giving pilots an advantage against any adversary and enabling them to execute their mission and come home safe."