North Korean leader Kim Jong Un is known to be an aviation enthusiast unlike his predecessors, his father and grandfather, who were aerophobic.
Besides being able to pilot small aircraft and travelling in his luxurious but ageing Russian-designed private jet, his love of flying was reported to have led to an overhaul of the regime's main airport three years ago. This was followed by its first air show in 2016.
The 34-year-old leader will surely have no problem flying to Singapore for the June 12 summit with United States President Donald Trump. But what is not so sure is whether Mr Kim's old private jet - a Soviet-made Ilyushin IL-62 from 1982 - can safely make the trip without stops.
Dubbed Air Force Un, the remodelled white jet with a North Korean emblem on its tailfin is reported to be able to fly up to 10,000km with a top speed of 900kmh.
Singapore is around 4,950km from Pyongyang, but experts have questioned if the plane can fly direct to the city-state, considering its age and the fact that it has not been tested for longer-haul journeys.
Modern jets can cover that distance in under seven hours.
Dr Lee Seong Hyon, director of unification strategy at the Sejong Institute think-tank in South Korea, said that Mr Kim can have a stopover in China or Vietnam to refuel "if there is any safety concern".
"As an alternative, Kim can pass through South Korean airspace, which reduces time. We will see," he told The Straits Times, noting that North Korea has already asked the International Civil Aviation Organisation for permission to use South Korean airspace "just in case".
Flying through South Korea is banned under current United Nations sanctions on North Korea.
Speculation has also risen that a third party, such as North Korea's only ally China, could offer a ride.
Dr Lee ruled out the US sending a plane due to security concerns. He said that "North Korea perceives Singapore as a neutral country", and Mr Kim's family members had in the past visited the Republic. An option might be for Singapore to offer "complimentary flight service as the host of this summit".
But Mr Shawn Ho, associate research fellow at the S. Rajaratnam School of International Studies in Singapore, said it was "quite unlikely from a political, logistical or cost point of view" for Singapore to do so - on top of hosting the summit.
A more viable option, he said, was for Mr Kim and his entourage to fly on their own to Beijing, and then transfer to another aircraft provided by a third party.
"Maybe the Chinese can provide the plane, so as to show support for North Korea. It will send a political and symbolic message that China is a friend and will be there when North Korea needs them," he said.
Mr Kim met Chinese President Xi Jinping twice this year, first in Beijing in March and then in the north-eastern port city of Dalian early last month. The North Korean leader was reported to have flown on his private jet to Dalian.
Manufactured by Ilyushin between 1963 and 1995, the four-engine IL-62 was once the world's largest airliner.
The one belonging to Mr Kim - officially named Chammae-1 after a species of hawk - was acquired before UN sanctions prohibited North Korea from importing aircraft.
It was first unveiled to the North Korean public in May 2014 in state-released photos which showed Mr Kim and his wife Ri Sol Ju disembarking.
A second batch of photos released in February 2015 showed Mr Kim seated on a plush-looking armchair on board the aircraft.
Earlier this year, it was used to transport a North Korean delegation, including Mr Kim's sister Kim Yo Jong, to the South to attend the Pyeongchang Winter Olympics.
Two planes could be involved in ferrying Mr Kim and his entourage to Singapore, said Mr Ho. Two North Korean planes were reported to have been sighted at Dalian airport - an IL-62 and a cargo plane operated by North Korea's state-owned airline Air Koryo - during the North Korean leader's recent visit.
Mr Ho said Mr Kim would probably travel to Singapore with his sister as well as other top aides, including his right-hand man, General Kim Yong Chol, who met Mr Trump in Washington last week.
Gen Kim Yong Chol was reported to have used an Air Koryo plane to arrive in Beijing before switching to an Air China flight to arrive in New York before going to the US capital.
