Thousands visited Kalaeloa Airport Saturday for a glimpse of the first plane circumnavigating the globe under solar power before it departs for the continental U.S. in about two weeks.

It was a rare up-close peek at the Solar Impulse 2, an aircraft developed by two Swiss explorers, that has flown from Abu Dhabi to Hawaii over several legs since March 2015. The plane is scheduled to leave Hawaii when the weather is favorable, anytime from April 15. The destination has been narrowed down to San Francisco, Los Angeles or Phoenix.

“It’s just astonishing what solar can do,” said Kapolei resident Wendy Renee, visiting the single-seat craft in Hangar 111. “I’m just flabbergasted by the fact that it’s flying by solar.”

Steven Minakami, a Kaneohe resident visiting with Renee, compared seeing the Solar Impulse 2 in person to watching the Wright Brothers’ first successful flight more than 100 years ago.

“This is just a start into the new technologies that will bring aviation into a much cleaner transportation mode,” said Minakami, an electrical engineer. “Just to see that someone was able to achieve it, at great expense of course, and at great size — for being so bulky. In the future, they may be like regular Cessna-looking aircraft.”

But unlike the Wright Brothers’ experiments, the Solar Impulse 2 is a global project with an international staff of young people traveling along the journey to support it.

Stephane Collet, a 25-year-old Swiss national, is one of about 15 people on the ground crew that helps the plane land and take off.

The ground crew pushes the plane, which has only one forward and one rear wheel, onto the runway. Crew members run along with the craft, holding the wings level until the pilot opens the throttle.

“It’s like if you launch a paper plane, you have to run with it and then you just leave it and you see it flying,” Collet said. “It’s a great feeling.”

The Honolulu-to-continental U.S. leg will be piloted by Bertrand Piccard, a Swiss psychiatrist who came up with the idea for a global solar flight to promote solar energy more than a decade ago. It will take about four days to complete this leg with only Piccard on board.

His co-founder, Swiss engineer Andre Borschberg, flew the five-day, Japan-to-Honolulu leg last summer, setting world records for the longest solo and solar flight.

Victoire Margairaz, a spokeswoman for the project, said Piccard has been preparing for the trans-Pacific flight with cardio workouts and self-hypnosis, which helps him relax and focus his mind, since pilots are able to sleep only about 20 minutes at a time during the flight.

The plane, being experimental and kept at a minimal weight, doesn’t have autopilot, but it does have stabilizers that can operate for only about 20 minutes before a human has to take control.

Bob Canali, an air traffic controller at Honolulu Airport, brought his wife and two children to see the craft.

He said before the plane arrived in July, air traffic controllers were given a briefing because of the special air separation the craft needs for protection. He said planes typically have about 1,000 feet of space above and below, but the Solar Impulse 2 receives about twice as much space because the wake turbulence will throw the craft around.

While working, he’s seen the plane on its practice runs on his radar as a slow-moving blip, striking for its incremental pace (It flies at about 31 mph).

“This one is really slow, like holy moly you’re still there,” he said. “It’s not like any other airplane we look at. I had to come out and see it for myself. That thing is the slowest thing in the air.”

“This thing is huge,” said Canali of the 78-yard, solar cell-covered wing — larger than a Boeing 747’s.

His children were initially mildly impressed, but picked up on its significance.

“What about in the night?” his 10-year-old daughter, Mira, asked, before recalling the batteries and saying one day she might fly on such a plane.

“They’re going to invent more,” she said.

“This is like a prototype of something that when (my kids) have kids will probably be more commonplace,” Canali added. “You can tell your kids, ‘I went and saw the original one.’”

The Solar Impulse 2 is expected to reach Abu Dhabi sometime this summer.

The stay in Hawaii was unexpectedly long because of battery trouble.