History was made earlier today when the first manned round-the-world flight powered entirely by solar energy was completed.

The solar-powered circumnavigation kicked off in Abu Dhabi back in March 2015, and the journey was originally supposed to finish around five months later in August. But a combination of weather and technical faults led to significant delays, and the Solar Impulse 2 aircraft spent most of last winter in a Hawaiian hangar.

The 40,000km flight was shared between André Borschberg and record-breaking hot air ballooner Bertrand Piccard, who alternated the 17 legs of the journey between them. The longest stint in the air took place between Japan and Hawaii, which, at 4,000 miles, also beat the record for the longest uninterrupted solar-powered flight.

The final leg of the journey kicked off in Cairo on July 24, and the aircraft touched down in Abu Dhabi 48 hours and 37 minutes later. The plane has spent a total of 23 days in the air to reach its goal.

It’s been six years since the first manned solar plane was unveiled to the world, with the first flight taking place shortly after.

The Solar Impulse’s journey has been fraught with delays since its inception, however, given that its first round-the-world attempt was originally scheduled to take place by 2012. The aircraft managed some smaller-scale jaunts over the years of testing, including a San Francisco to New York trip back in 2013 that took two months and a handful of stopovers to complete.

The plane sports a 72-meter wingspan — wider than a Boeing 747 jumbo jet — this width allows for the 17,000 solar cells that power the lithium-ion batteries for nighttime flying on the Solar Impulse 2. The journey may have taken significantly longer than planned, but it has been a colossal achievement, one that will go down in the aviation history books.

But more than that, the flight shows the potential of renewable energy. And that was the point of the venture all along — to demonstrate what can be achieved without relying on fossil fuels.

Last week, Facebook’s solar-powered plane also completed its first full-scale test flight — however, it’s essentially an unmanned drone with the express purpose of beaming internet access to hard-to-reach areas.