SINGAPORE- Solar Impulse 2 landed on Tuesday (July 26) in the United Arab Emirates, completing its epic journey to become the first sun-powered airplane to circle the globe.
The plane touched down at 4.05am local time (8.05am Singapore time) in the capital Abu Dhabi, accomplishing a mission which began in March last year to promote renewable energy.
The Straits Times looks back at Solar Impulse 2's amazing voyage:
1. What is so special about Solar Impulse 2?
It is not the first solar airplane, but Solar Impulse 2 and its prototype - Solar Impulse - were the first to fly day and night without any form of fuel, using only energy stored in its batteries.
Even before it completed its world trip, the Solar Impulse project has broken a number of solar aviation records along the way. For example, it completed the first solar flight between two continents, and the first solar flight to cross an ocean.
In a five-day flight between Nagoya, Japan, and Hawaii in July last year, it broke the record for the longest distance and time any solar aircraft has flown.
Pilot Andre Borschberg also broke the record for the longest solo flight without refuelling in any aircraft by flying 117 hours.
2. How does the plane function?
It has a wingspan of a Boeing 747 Jumbo Jet, the weight of a family car and the power of a small motorcycle. It is the largest aircraft ever built with such a low weight.
It has 17,248 solar cells, a carbon fibre frame and a small cockpit of 3.8 sq m - 1.5 times the size of a 2013 Mini Cooper.
The cockpit has just enough space for oxygen supplies, food and survival equipment lasting several days.
3. Who built the plane?
Co-pilots Bertrand Piccard and Andre Borschberg drove the construction of the plane, with the help of a team of about 90 people, including engineers, technicians and mission controllers. They are supported financially and technologically by over a hundred partners and advisers.
Since 2003, the project has cost at least €170 million (S$254 million), raised from individuals, corporate sponsors and the Swiss government, which contributed €5 million.
4. What were some of the stops on the round-the-world trip?
The flight capped a remarkable 42,000km journey across four continents, two oceans and three seas.
The journey, which began from Abu Dhabi on March 9, 2015, covered Oman, India, Myanmar, China, Japan, the United States, back to Europe and Abu Dhabi.
The plane was scheduled to return to Abu Dhabi in August 2015, but met some delays on the way - the most serious one caused by too much sun.
During its longest leg from Japan to Hawaii, the plane's batteries overheated and were replaced.
After the batteries were replaced, the pilots had to wait for the next flying season to come around this year before it was safe to attempt the Atlantic crossing.
5. Who are the pilots?
Bertrand Piccard, 58 and Andre Borschberg, 63, who are both Swiss.
Achieved in several legs, both of them have accumulated around 500 flight hours in the tiny cockpit.
Piccard is a psychiatrist, explorer and aeronaut while Borschberg is an engineer, a fighter pilot as well as a professional airplane and helicopter pilot.
Piccard, and his co-pilot Brian Jones, were the first men to circumnavigate the world non-stop in a hot air balloon in 1999.
6. Can we expect commercial solar-powered planes soon?
Piccard has called the aircraft a "flying laboratory".
"We are testing all these new, clean and modern technologies in order to fly with an endless endurance," he said.
While the pilots do not expect commercial solar-powered planes any time soon, they hope the project will help spur wider progress in clean energy.
"We have new insulation material, new LED lamps, we have new extremely light carbon fiber structures... All this can be used now on the ground," dividing "by two the energy consumption and therefore the CO2 emissions of the world", Piccard said.
Find out more about Solar Impulse 2's epic journey here.
Sources: AFP, BBC, The Guardian, Solar Impulse website