|Solar Impulse 2|
A ground-breaking plane has defied expectations by travelling 25,000 miles (40,200km) around the world without a single drop of fuel.
The solar-powered aircraft, Solar Impulse 2, successfully completed its flight today, returning to Abu Dhabi after an epic 17-month journey.
With a wingspan larger than a Boeing 747, the ground-breaking craft touched down in the United Arab Emirates capital at 4:05am local time.
Swiss pilots Bertrand Piccard (right) and Andre Borschberg celebrate after landing their solar-powered aircraft in Abu Dhabi. dailymail
Solar Impulse touches down in Abu Dhabi after its iconic journey around the world without using a single drop of fuel
Solar Impulse 2 approaches to land at Al Bateen Executive Airport in Abu Dhabi, where it first took off more than a year ago
The plane first took off from Abu Dhabi on March 9 of last year, beginning a landmark journey of around the globe and nearly 500 hours of flying.
Unfavorable weather at times hindered smooth flying, causing the plane to be grounded for months in some countries.
At 2:44am, the Solar Impulse Twitter account wrote: 'BREAKING: we flew 40,000km without fuel. It's a first for energy, take it further! #futureisclean'
Before taking off, Bertrand Piccard, who piloted the final leg, said: 'It's a project for energy, for a better world.'
Betrand Piccard (right) and Andre Borschberg (left) celebrate after landing in Abu Dhabi on the final leg of their epic journey. dailymail
A photo taken from Solar Impulse 2 shows an amazing aerial view of the Red Sea on its flight on 24 July
BERTRAND PICCARD AND ANDRE BORSCHBERG ANSWER QUESTIONS ABOUT THEIR RECORD BREAKING FLIGHT
The plane flew over the Golden Gate bridge in San Francisco on April 23, 2016
How does it feel to have finished?
Mr Borscheberg said: 'I am only starting to realise that it is over now. But it is always the right time. The flight being over does not mean the project is over.
'We have a solid base now to work in the different directions we hope to work in.'
What is your next step going to be?
Mr Piccard: 'For aviation we are going to continue to use our expertise and knowledge to develop high altitude, unmanned solar aircraft and maybe even electric airplanes.
'I want to create a world council of clean technology to bring together all the experts in that sector who are normally not communicationg.
'I want to create a single voice where these experts can talk to the governments and heads of states about clear solutions that can fight climate change while also creating jobs for industry.
'There are a lot of interesting things to do. We are not unemployed and we are certainly not on vacation now.'
Could airlines soon use solar powered aircraft to carry passengers?
Mr Piccard said: 'We are not quite there yet for solar airplanes. But we will be there very soon with electric planes. I am certain that within 10 years there will be fully electric airplanes for 50 passengers on short to medium haul flights.
'It means there will be no noise and no pollution. For airports that are close to the city it will be a blessing for the neighbourhood and there will be new opportunities for air travel.'
You were in the air for days at a time, what was the hardest thing about such long flights?
Mr Piccard said: 'The most difficult moments were on the ground – preparing the technology, finding the partners with the funding, getting the permission and dealing with the bureaucracy and good weather conditions to fly.
'But once you are in the air it was magical, it was fantastic. I am looking at my propellers turning on the left and right wing, then I look at the sun and I understand it is only the energy of the sun that gives the energy for these motors to turn. It is science fiction but it is a science fiction that is happening today.
'It was never boring flying in that plane. It is completely quiet, completely clean and completely new. There is only one plane like that in the entire world.
The plane travelled over Hawaii as part of a test flight in March 2016
'It was a privilege to fly it.'
Mr Borscheberg added: 'I really worked on the cockpit design and did it in such a way so I could practice at least part of the yoga I do every day. While I couldn't do sun salutations, for example, as I could not get up but I could do some of the exercises.
'Interestingly it became my home and the place where I lived. I got attached to this environment so when I went down after landing it was like leaving an old friend who had taken me over the ocean.'
How do you go to the toilet on such long flights?
Mr Piccard said: 'Inside the seat there is a bag and you open the seat and go in there.
'But I tell you it is beautiful sitting on the toilet there, I have the most beautiful view of the world in front of you. You don't even need to close the curtains as there are no neighbours.'
What was your greatest highlight in the journey around the world?
Mr Borscheberg said: 'I read so much about pioneers when I was boy. The flight we did from Japan to Hawaii was THE exploratory flight of the project. I knew I wanted to do it.
'It was long and difficult, and we had some technical difficulties right up until before I took off. It was not easy but it will be an experience I will never forget.'
Swiss explorers Bertrand Piccard and André Borschberg, took turns piloting the aircraft, which can fly for days on only energy from the sun using an array of solar panels on its wings to charge on board batteries.
The plane's wingspan is longer than a jumbo jet but its light construction keeps its weight to about as much as a car.
It typically travels at a mere 30mph (48km/h), although its flight speed can double when exposed to full sunlight.
Speaking to MailOnline after landing, Mr Piccard said: 'Coming into Abu Dhabi was really a great moment. I had great emotion at finishing this last leg of our round-the-world journey – a project that has taken over my life for 17 years.
'But at the same time we had a lot of thermals and turbulence around Saudi Arabia, so I had to concentrate and focus on flying.
'I could not be overwhelmed by what we had achieved. It always seems like in big adventures like this there is always a final test.'
Solar Impulse 2 pilots Bertrand Piccard (left) and Andre Borschberg speak about their journey after landing in Abu Dhabi
The Solar Impact 2 started its round-the-world solar flight from Abu Dhabi in March 2015, finally returning to base 16 months later
Swiss explorers Piccard and Borschberg are also the founders of Solar Impulse, which seeks to bolster support for clean energy
The final descent into Abu Dhabi marked the end of Solar Impulse's 24,500 mile journey around the world
The Swiss team is campaigning to bolster support for clean energy. The propeller-driven aircraft's four engines are powered exclusively by energy collected from more than 17,000 solar cells built on the plane's wings.
Life on board the Solar Impulse 2 was very cramped, with the cockpit measuring just 40.9 square feet (3.8 square metres).
This meant that it had enough room for instruments, some food and a reclining chair.
During footage, filmed for Wired, Mr Piccard took a selfie of him and his giant plane, before bringing the camera inside the cockpit to show off the aircraft's controls.
SOLAR IMPULSE 2'S ROUND THE WORLD JOURNEY
The globe-circling voyage began in March 2015 from Abu Dhabi, the capital of the United Arab Emirates, and made stops in Oman, Myanmar, China and Japan.
Piccard and Andre Borschberg took turns piloting the plane on each leg of the journey.
Both trained to stay alert for long stretches of time by practicing meditation and hypnosis.
Borschberg set a new endurance record for the longest non-stop solo flight last July during a 118-hour trans-Pacific crossing, over five days and five nights, from Japan to Hawaii.
He showed how he can recline in his seat to turn it into a bed, and filmed his modest food supplies.
Speaking to MailOnline, Mr Piccard said the cockpit had become more like a home.
He said: 'You do everything in that cockpit. You have a seat that you can recline in order to sleep flat. You open the seat to go to the toilet, you have food either side of the seat, you can heat your food, wash yourself with wet wipes and change your clothes.
'Really it is like a little house. When I get out of the cockpit I feel homesick.'
The pilots were only able to sleep for 20 minutes at a time, and used alarms to make sure they did not doze for longer.
Both pilots trained to stay alert for long stretches of time by practicing meditation and hypnosis.
The pilots were met with a huge reception, including a marching band to welcome them to Abu Dhabi
An aerial image shows Solar Impulse 2 during its landing in Abu Dhabi having finished its round-the-world flight
Monaco's Prince Albert II attends a press conference following the landing of the solar-powered plane, alongside State Minister and chief executive officer of the Abu Dhabi Future Energy Company (Masdar), Sultan Ahmed al-Jaber (far right), and pilot Bertrand Piccard
Solar Impulse 2, seen here flying over Egypt's Giza pyramid complex, has successfully completed the first fuel-free flight around the world
Having completed their huge journey around the world, pilots Bertrand Piccard and Andre Borschberg celebrated together
Technicians prepared the solar-powered Solar Impulse 2 aircraft at the Cairo International Airport on July 23 before it took off for its final flight in its round the world journey, an effort which has taken over a year to complete
The plane took off from Abu Dhabi in March 2015 and journeyed around the globe in a landmark voyage of about 24,500 miles
A map shows the route of Solar Impulse 2 around the globe as the plane left Cairo on Sunday to complete the last leg of its journey
HOW DOES SOLAR IMPULSE WORK?
Solar Impulse 2 is powered by 17,000 solar cells and on-board rechargeable lithium batteries, allowing it to fly through the night.
Its wingspan is longer than a jumbo jet but its light construction keeps its weight to about as much as a car.
Solar Impulse 2 relies on getting enough solar power during the day to survive the night.
It is also extremely light - about the weight of a car - and as wide as a passenger jet.
Both of these combined means it is extremely susceptible to the weather.
In high winds it can struggle to stay aloft at the altitudes necessary to gather sunlight.
Excess energy was stored in four batteries during daylight hours to keep the plane flying after dark.
Over its entire mission, Solar Impulse 2 cruised at altitudes of up to 5.5 miles (9 km) and at an average speed of between 12.5 and 25 miles (45 and 90 km) per hour.
However in high winds, the plane struggled to stay aloft at the altitudes necessary to gather sunlight.
The crew of the solar-powered plane was greeted upon arrival at Al Batin Airport in Abu Dabi to complete its world tour flight
Pilot Bertrand Piccard was at the controls of the single-seater when it landed at the Al Bateen Executive Airport in Abu Dhabi
The plane had 16 stopovers along the way including in Oman, India, Myanmar, China, Japan, the United States, Spain and Egypt.
Abu Dhabi's green energy firm, Masdar, is the official host partner of Solar Impulse 2.
Oil-rich Abu Dhabi is investing billions in industry, tourism and renewables to diversify its economy away from oil.
Mr Borschberg and Mr Piccard have said they want to raise awareness of renewable energy sources and technologies with their project, although they do not expect solar-powered commercial planes any time soon.
'There will be passengers very soon in electric airplanes that we will charge on the ground,' Mr Piccard had said when the plane arrived in Cairo.
'On the ground you can charge batteries and you can have short haul flights, maybe 500 kilometres with 50 people flying in these planes in a decade', he predicted.
Solar Impulse landed in Cairo earlier this month as it headed to its final stop in Abu Dhabi
Over its entire mission, Solar Impulse 2 cruised at altitudes of up to 5.5 miles (9 km) and at an average speed between 12.5 and 25 miles per hour