AF1 stopped twice for fuel…
"Trump arrived late Tuesday in Air Force One after a long flight that included refueling stops in England and Qatar."
sauce: http://www.msn.com/en-xl/asia/top-stories/trump-kim-in-hanoi-for-second-round-of-nuclear-talks/ar-BBU56Bx
"At approximately the same time Air-Force One was completing a refueling in England (RAF base Mildenhall, just Northeast of London). Next stop, Hanoi."
NO mention of QATAR
https://theconservativetreehouse.com/2019/02/25/hanoi-summit-update-chairman-kim-arrives-in-vietnam-potus-trump-refuels-in-england/