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Whether the emergence of drones watching us, shipping our items or doing our bidding inspires fear or excitement, it’s no question that the drones are coming (one day) and they’ll need energy to keep them aloft in the sky. On Monday, defense company AeroVironment and venture-backed solar startup Alta Devices announced that they’ve collaborated on a prototype drone that uses Alta’s efficient and lightweight solar panels in conjunction with batteries to extract and store energy from the sun.

The team said that in a test run of the drone, they flew it for 9 hours and 11 minutes — a record flight, and 350 percent longer than more standard drones. The drone can run for more than 3 hours without solar power using the drone’s batteries.

Endurance in the sky could be particularly important for customers like the military that use drones for critical missions. On a more somber note, drone strikes from the U.S. government have killed people in Yemen in recent days.

Alta Devices told us earlier this year that it has been building solar modules for applications for both soldiers and for drones that spy on and attack enemies. Alta’s solar panels are made from gallium arsenide, instead of silicon, and they’re much thinner than typical solar panels. As a result they’re more expensive than standard ones, but also more lightweight and efficient.

But that also means they’re less attractive for much of the rooftop solar panel market. However Alta’s panels could be a good fit for soldiers that might have to carry the panels on their bodies, or drones that have to carry them through the air. Alta claims that its solar chargers could reduce a soldier’s battery heft by 70 percent, or roughly 25 pounds.

Alta Devices was founded in 2007 and has raised $120 million in venture capital from investors such as Kleiner Perkins and Dow Chemical. The company has been planning to raise a new round of funding this year to build a 40MW factory, which could end up being located in Asia.