The Washington Post brings up an embarrassing detail that may need to be cleared up before the historic summit between President Donald Trump and North Korean dictator Kim Jong-un can take place: Kim may not have an airplane capable of crossing the Pacific to attend a meeting in Europe, at least not without an embarrassing number of refueling stops.

“We used to make fun of what they have—it’s old stuff. We would joke about their old Soviet planes,” Bush-era CIA analyst Sue Mi Terry told the Post.

There are plenty of possible venues for the meeting that Kim could reach easily, but reading between the lines, one senses the suspicion that Trump could propose a location like Switzerland in part because Kim would then be obliged to either accept a humiliating lift from a third party like South Korea or China—probably in an aircraft stuffed with surveillance devices—make the humiliating admission that North Korean aerospace technology is incapable of providing him with secure and timely transportation to Europe, or attempt a humiliating and possibly dangerous journey in a vintage Cold War-era plane built by the people who lost the Cold War.

The Post notes the dichotomy of a rogue nation that threatens the world with miniaturized nuclear warheads on intercontinental ballistic missiles but is incapable of delivering its oversized dictator to an international summit meeting.

There is also the question of whether Kim Jong-un shares his father Kim Jong-il’s aversion to flying, given his similar use of a train to visit Beijing last month. The current dictator has taken some steps to demonstrate that he likes airplanes, but the North Koreans may regard flying as too great a security risk for their maximum leader, or they wish to convey the notion that certain hostile foreign powers cannot be trusted not to blow Kim’s plane out of the sky.

The bigger picture of arranging the Trump-Kim summit is fascinating, given that the timeframe for hammering out the details of the most sensitive meeting in the modern era is relatively short. The New York Times on Wednesday quoted South Korea’s President Moon Jae-in, who is scheduled to meet with Kim on April 27, saying that the U.S. and North Korea are negotiating with “will and sincerity” to make the Trump-Kim meeting happen. Trump himself said on Monday that U.S. and North Korean officials are working to set the meeting up in May or early June. Both Trump and Moon indicated that the location of the meeting has yet to be determined.

The NYT reviewed possible venues mentioned by officials and media sources:

It is unclear whether Mr. Kim would be daring enough to visit Washington, which North Korea has for decades accused of plotting to invade it. And Mr. Kim’s private jets are said to lack the fuel capacity for a nonstop flight to Washington from Pyongyang.

The idea of a summit meeting in Pyongyang makes some American officials cringe, envisioning how North Korean propagandists would depict it as Mr. Trump paying homage to Mr. Kim. Some officials have also expressed reluctance to hold the talks in South Korea or at Panmunjom, the “truce village” on the inter-Korean border where Mr. Kim and Mr. Moon will hold their talks; the American officials said they would prefer a neutral site that did not highlight the South’s role in facilitating the talks.

News reports in South Korea and the United States have mentioned Geneva and the Mongolian capital, Ulan Bator, as possible venues.

Administration officials told CNN last week that “secret, direct talks” with North Korean officials have been underway for some time, including participation by CIA Director Mike Pompeo, who is transitioning to Secretary of State.

According to CNN’s sources, the North Koreans would prefer to hold the meeting in Pyongyang, but it is “unclear whether the White House would be willing to hold the talks there.”

Ulaanbaatar pops up in almost every discussion of the summit as a leading contender, which might seem like an odd choice, but Business Insider explains there are sound reasons for considering it: “Mongolia has hosted meetings between North Korea and Japan in the past and is on friendly terms with most countries, including its neighbors Russia and China, as well as both the US and North Korea.”

Also, BI notes that Ulaanbaatar is the world’s coldest capital city and “inhospitable for large chunks of the year,” so “hotels and transport may have more availability than other cities to potentially manage a last-minute influx of diplomats and press for the Trump-Kim summit.” Kim could make the journey by train, while Trump would get to fly into Genghis Khan International Airport.