A Swiss balloonist and a Swiss air force pilot hope to fly the first solar-powered plane around the world starting next week, and the most challenging leg of the trip will be a five-day flight from China to Hawaii.

Only one of the two pilots — either Bertrand Piccard, 56, or Andre Borschberg, 60 — will be packed into the tiny cockpit on the 5,000-mile journey from Nanjing, China, to the Kalaeloa Airport in West Oahu.

Weather, technology and human endurance permitting, the solar plane should touch down in Hawaii on April 20, adding one more page to Hawaii’s storied aviation history.

Kalaeloa Airport is a fitting destination since it is also known as John Rodgers Field, named after the Navy commander who in 1925 made the first trans-Pacific flight from California to a point near Honolulu.

Hawaii will be the first destination in the United States for the plane, known as the Solar Impulse 2. After 12 years of preparation, from studies to a prototype at the Solar Impulse headquarters in Switzerland, the Solar Impulse 2 builders believe it is ready to fly over 25,000 miles beginning and ending in Abu Dhabi in the United Arab Emirates.

"The crossing of the Pacific is an enormous challenge in both technical and human terms," Solar Impulse said in a written statement.

The sun will be the only source of energy for the aircraft, as the plane’s 72-meter wingspan was built with more than 17,000 solar cells, four electric motors and lithium batteries replacing the need for fossil fuel.

The initial takeoff is scheduled for March 3. It was pushed back from Sunday due to sandstorms in Abu Dhabi.

The launch and landing dates can easily shift because the light aircraft, at 5,000 pounds or about the weight of a car, is more vulnerable to turbulence and other weather conditions, said Peter Forman, an aviation historian based in Hawaii.

"To build an airplane that is this light and this big, it must be built with just the very lightest materials. It is not a very strong airplane," Forman said. "This is going to be a very difficult challenge, flying that plane around the world, because of the weather."

Solar Impulse 2, with a wingspan larger than a Boeing 747’s, lands and takes off at 30 miles per hour, a speed more than four times slower than a commercial airliner, Forman said.

"A plane that big, taking off and landing at 30 miles per hour, is quite something," he said. "It is moving very slowly for something that large."

The Solar Impulse team will stay two or three days in Hawaii for aircraft maintenance, a press conference and public visits.

After Hawaii the Solar Impulse 2 will fly to Phoenix, then an as-yet-undetermined stop in the Midwest, followed by a landing in New York.

The flight to Hawaii will test the solar cells’ capability, said Maxine Ghavi, senior vice president and head of the solar industry segment initiative at ABB, the Zurich-based renewable energy engineering company that helped build the plane.

"Our engineers have helped update maximum power point tracking devices, or MPPT, that reap maximum power regardless of atmospheric conditions from 17,248 razor-thin solar cells that cover the plane’s wings in a solar skin," Ghavi said. "These are critical, since failure of just one during the five-day, nonstop flight between China and Hawaii, the mission’s longest leg, could make it difficult to charge batteries sufficiently during daylight while driving motors to reach maximum altitude necessary for the nighttime flight."

During the day when the solar panels are generating power, the plane will climb to over 27,000 feet. At night it will run on battery power and gradually drop to below 5,000 feet.

About 50 engineers and technicians, 80 technological partners and more than 100 advisers and suppliers contributed to the prototype and the final plane.

To remain focused on operating the plane, the pilot will practice yoga, meditation and self-hypnosis as he sits in a cockpit 4 feet wide by 61⁄2 feet long. The pilot’s seat doubles as a toilet.

"Solar Impulse is not just a technological adventure. It is also a human adventure in which acceptance of the real world is a necessity and sleep management is a part of reality," the company said in a written statement. "It was realized that professional support on a holistic level to support physical, psychological, emotional and spiritual challenges would be required."

The plane will have six oxygen bottles, a parachute, a life raft and a week’s worth of food and water on board, as the pilots will be in the air a combined 500 hours — more than 20 days.

The Solar Impulse 2 flight is not the first world trip for Piccard. The founder and chairman of Solar Impulse completed a nonstop, round-the-world balloon flight in 1999.

Borschberg graduated from the Massachusetts Institute of Technology and is the CEO of Solar Impulse. He trained as a pilot in the Swiss air force, flying for 20 years. He is also an entrepreneur who started Innovative Silicon, a microprocessor company.

In July 2010 Borschberg successfully flew the Solar Impulse day and night, operating the plane for 26 hours.