North Korean leader Kim Jong-un was spotted Monday traveling by his family train on his way to a summit with Russian President Vladimir Putin.

The third-generation Kim diverged from his famously flight-phobic father in his past summit trips, in June 2018 flying Air China to get to Singapore for the landmark meeting with then-US President Donald Trump. This time he chose to travel 20 hours on the train that is speculated to be bulletproof and multifunctional, with luxurious decors.

Rep. Tae Yong-ho, who was a senior diplomat for North Korea before defecting to the South in August 2016, told The Korea Herald on Tuesday that “safety is likely the biggest factor” in Kim opting for the long train ride.

Kim has flown short distances domestically in recent years, but not overseas, the defector-turned-lawmaker said. His Soviet-era family jet, the Chammae-1, is too old and probably hasn’t been refurbished properly.

“Besides, he can easily load all the things he is going to be needing, including his state cars, on the train. That’s what he did on his Hanoi trip back in 2019,” he said.

Tae said Kim’s train has “a very luxurious interior,” as widely rumored to be, and “everything that the North Korean leader may need,” he said. “It’s equipped with all the facilities that let Kim to do his job as usual, as if he had never left Pyongyang. So it’s like his mobile office.”

Some South Korean media reports have suggested the train is furbished with reception halls, conference rooms and advanced communication facilities as well as flat-screen TVs to assist Kim in carrying out his duties, personal and official.

The lawmaker said that although the train is “built to be as bulletproof as possible,” it is probably not a stealth train as some media outlets speculate. “The train isn’t exactly state-of-the-art, by outside standards,” he said.

Rep. Shin Won-sik, a former Army general and the executive secretary for the National Assembly national defense committee, agreed that the train that’s taking Kim to Russia is not a stealth train.

“We don’t have stealth trains, and neither does the US, as far as I know,” he told The Korea Herald. “North Korean leaders have traditionally traveled by train. Being in the air can make you an easy target.”

Traveling by train is “the norm and tradition” for North Korean leaders, said Yang Uk, a national security researcher at the Asan Institute for Policy Studies.

“It’s nothing out of the ordinary at all that he is traveling to Vladivostok, which is not that far a destination to begin with, on a train,” Yang said.“Although Kim Jong-un himself seems to have no aversion to flying, he has taken trains more often looking at his earlier trips outside North Korea.”

Kim is thought to be seeking military and technical support from Russia through his summit with Putin, according to Rep. Kwon Young-se, the previous minister of unification who exited the Cabinet and returned to the ruling People Power Party in July.

Speaking to The Herald, the ex-minister said that he believes both sides may have needs that they could be fulfilling for one another. He said that Kim may be on the lookout for technical assistance from Russia, possibly including one concerning the twice-failed launch of the spy satellite, while Putin may ask North Korea for weapons for the war in Ukraine.

He added that the summit is also an apparent response to South Korean President Yoon Suk Yeol‘s strengthening of trilateral cooperation with the US and Japan.