Andre Borschberg, pilot of the plane attempting to fly around the world powered only by the sun, was in fine spirits after four days in the air and is excited to be landing in Hawaii Friday at sunrise.

“Feeling great and so excited that we are slowly getting to your islands,” Borschberg, 62, said Thursday morning in an interview with the Honolulu Star-Advertiser from the cockpit of the Solar Impulse 2 while en route to Oahu. “It is a fantastic moment.”

“The arrival is set for tomorrow (Friday) morning at sunrise. It is a special moment for us because it is the first airplane that can fly day and night, a week nonstop, even a month on solar energy,” Borschberg said. “It will be a pleasure to discover Honolulu at sunrise.”

Borschberg, CEO of Solar Impulse 2, is expected to land around 6 a.m. Friday after completing the longest and most dangerous leg — from Nagoya, Japan, to Honolulu — of the round-the-world journey.

Borschberg, who had been airborne for more than 100 hours as of Thursday morning, has already broken the record for duration of a solo flight without refueling, surpassing the mark set in 2006 by American Steve Fossett, who flew around the world in 76 hours in the jet-engine Virgin Atlantic Global Flyer.

The Solar Impulse 2 and Borschberg have also broken all distance and duration world records for solar aviation, the plane’s sponsors said.

As of 6 p.m. Hawaii time Thursday, the Solar Impulse 2 had finished 91 percent of its journey to Oahu, completing 4,642 miles of the 40,806-mile journey.

A major challenge of the flight was making a home out of a cockpit that is 4 feet wide by 61⁄2 feet long, Borschberg said.

“The challenge is to be sustainable in this tiny environment — how to find a way to live and build a home in this tiny environment, this tiny cockpit, in a way so that you don’t get exhausted too quickly,” he said.

“In terms of food and functioning of the body, the challenge is to have food which can sustain the environment we have here, which is big variation in temperatures,” he said. “When I am very high it is minus 20 degrees (Celsius, or minus 4 Fahrenheit), and when I am down it is 27 (Celsius or 80 Fahrenheit).”

During the day when the solar panels are generating power, the plane climbs to over 27,000 feet. At night it runs on battery power and gradually drops to below 8,000 feet.

BORSCHBERG’S SEAT doubles as a toilet, the pilot said. “We have a toilet integrated into the seat which I do use every day.”

The goal of the historic flight is to show the capabilities of the solar technology that can be used for daily energy needs, said Borschberg.

“Aboard this airplane we have technologies we can use everywhere, the way we build homes, the way we build cars and the way we build appliances,” he said.

Borschberg said he hasn’t spent much time thinking about his arrival in Hawaii.

“I’ve been in the air for four days. I have been thinking mostly about the present moment about what I have to do. Not thinking about the destination because so many things could happen,” he said. “Now that it is the last day, I start projecting myself into the future. It’s a dream to be able to reach it … with a solar-powered airplane.”

Bertrand Piccard, chairman and co-pilot of Solar Impulse 2, alternates with Borschberg as pilot and will be flying the plane from Hawaii to Arizona.

The flight is proving that “Piccard’s vision of reaching unlimited endurance without fuel was not a crazy dream,” the flight organizers said.

“Can you imagine that a solar-powered airplane without fuel can now fly longer than a jet plane?” said Piccard. “This is a clear message that clean technologies can achieve impossible goals!”

The sun is the only source of energy for the carbon-fiber aircraft. The plane’s 236-foot wingspan was built with more than 17,000 solar cells, four electric motors and lithium batteries replacing the need for fuel.

HAWAII WILL BE the first of four U.S. destinations for the plane. The Solar Impulse 2 will take off for Phoenix from Hawaii and then make an as-yet-undetermined stop in the Midwest, followed by a landing in New York.

Since leaving Abu Dhabi, United Arab Emirates, in March, the plane has traveled to Muscat, Oman; Ahmedabad and Varanasi, India; Mandalay, Myanmar; Chongqing and Nanjing, China; and Nagoya, Japan.