The HB-SIA solar-powered plane took off from Switzerland today to make its first 24-hour test flight. During the day the plane's batteries will be charged with excess energy collected by its 12,000 solar cells and the goal is to see if it's possible to make efficient use of the battery energy to fly throughout the night.
The aim is to assess whether the plane can fly in darkness, using solar cells on its wings to generate enough power to stay in the air for 24 hours.
The HB-SIA plane, which took off from Switzerland, has the weight of a family car but the wingspan of a big airliner.
The prototype will then start a slow descent using energy stored in its batteries until sunrise.
"The big question is whether the pilot can make efficient use of the battery energy to fly throughout the night," the team said in a statement.
"If this mission is successful, it will be the longest and highest flight ever made by a solar plane."