"It's been a lot of fun. It's really cool," Guthmiller told Metro recently as he was mid-flight from Kuala Lumpur to Manila. "So many people have been so nice to me. Total strangers that find out what I'm doing think it's cool and take me out to dinner and show me around town."
He will travel roughly 29,000-miles on the trip that will last more than a month. He's expected to finish around the middle of this month, though delays are possible.
The South Dakota-native began flying at age 16 and has since earned his commercial pilot certificate. He's flying a small, single-engine plane, which had some of the seats removed to fit extra fuel tanks to increase the range. He's averaging at least nine hours of flight time each leg of his journey.
Besides some minor issues related to severe weather and some maintenance after mistakenly being given the wrong fuel, Guthmiller said the ride's been pretty smooth.
He's tweeted pictures of the view from his plane, which included pyramids in Egypt. He's also tweeted about having hours of Michael Bublé to listen to while making a seven-hour flight over the desert.
While seeing international cities that he's never visited before has been exciting, he said it's strange to be on his own.
"Getting to all of these places I thought of visiting over the years and then being by myself was really weird," he said. "I'm not there with a group of friends like I would have expected."
Guthmiller, an electrical engineer and computer science major, is seeking sponsors to help pay for the trip and then any money raised after that will help Code.org, a non-profit that tries to expand participating and availability of computer science.
Besides the money, Guthmiller is hoping his mission inspires others.
"The biggest thing I'm hoping to accomplish is to go out and inspire other people to do things. You go out and kind of break it down and figure out how to do it and you can do it," he said. "I don't think there's anything particularly special about me or me as a pilot … I just read about other kids doing it and figured I could do the same thing."
Ross Aimer, the CEO of Aero Consulting Experts and a retired United Airlines captain, said the flying solo part of Guthmiller's journey is not the hardest aspect; it's the support needed in planning and on the ground.
"There are still a lot of problems associated with this type of adventure that have to be over come, but if you've got a good team that can take care of all that stuff, then it can be done," said Aimer.
According to Guinness World Records, the youngest person to fly solo around the world is California-native Jack Wiegand who completed the trip at 21 years old.
Wiegand completed the trip in June 2013 in just under two months.
For Guthmiller, the journey is more than just the potential solo flight record.
"Ultimately … the biggest thing is not the record, just to hopefully inspire other people," he said.