ABU DHABI, United Arab Emirates >> The world’s first round-the-world flight to be powered solely by the sun’s energy made history today as it landed in Abu Dhabi, where it first took off on an epic 25,000-mile journey that began more than a year ago.

Since its March 2015 takeoff, the Swiss-engineered Solar Impulse 2 has made 16 stops across the world without using a drop of fuel to demonstrate that using the plane’s clean technologies on the ground can halve the world’s energy consumption, save natural resources and improve quality of life.

After landing the plane, pilot Bertrand Piccard was greeted outside the cockpit by his Solar Impulse partner and fellow pilot Andre Borschberg. They hugged and pumped their fists in the air.

“The future is clean. The future is you. The future is now. Let’s take it further,” Piccard said, speaking through a microphone to applause and cheers from a crowd that included Prince Albert of Monaco.

The aircraft is uniquely powered by 17,248 solar cells that transfer energy to four electrical motors that power the plane’s propellers. It runs on four lithium polymer batteries at night. The plane’s wingspan stretches 236 feet to catch the sun’s energy.

At around 5,070 pounds the plane weighs about as much as a minivan or midsize truck. An empty Boeing 747, in comparison, weighs 400,000 pounds. To help steady it during takeoffs and landings, the plane was guided by runners and bicyclists.

Despite its historic mission, the Solar Impulse 2’s journey was far from quick or problem-free.

The pilots faced a nine-month delay a year ago after the plane’s batteries were damaged during a flight from Japan to Hawaii. (Solar Impulse landed at Kalaeloa Airport on July 3, 2015, from Japan after five days and nights in the air — the longest solar flight both by time and distance. The plane departed Kalaeloa on April 21.)

It was also delayed for more than a week in Cairo ahead of its final flight to Abu Dhabi when Piccard fell ill, and due to poor weather conditions.

Over its entire mission, Solar Impulse 2 completed more than 500 flight hours, cruising at an average speed of between 28 and 56 mph. It made stops in Oman, India, Myanmar, China, Japan, the U.S., Spain, Italy, Egypt and the United Arab Emirates. Its North American stops included California, Arizona, Oklahoma, Ohio, Pennsylvania and New York.

The carbon-fiber plane is a single-seater aircraft, meaning its two Swiss pilots — Piccard and Borschberg— had to take turns flying solo for long days and nights. To calm their minds and manage fatigue during the long solo flights, Borschberg practiced yoga and Piccard, self-hypnosis.

In a statement this week, Borschberg said it is no longer a question of whether it’s possible to fly without fuel or polluting emissions.

“By flying around the world thanks to renewable energy and clean technologies, we have demonstrated that we can now make our world more energy-efficient,” he said.

The pilots would rest a maximum of 20 minutes at a time, repeating the naps 12 times over each 24-hour stretch.

It took 70 hours for Piccard to cross the Atlantic Ocean, the first such flight by a solar-powered airplane.

Borschberg’s flight over the Pacific Ocean at 118 hours — or what is five days and five nights — shattered the record for the longest flight duration by an aircraft flying solo.

Neither pilot was able to stand in the cockpit while flying, but the seat reclined for stretching and its cushion could be removed for access to a toilet. Goggles worn over the pilot’s eyes flashed lights to wake him up, while armbands placed underneath their suits buzzed when the plane was not at flying level.

The plane also did not have a pressurized cockpit so Borschberg and Piccard could feel changes in temperature. The pilot’s blood oxygen levels were monitored and sent back to ground control in Monaco.