Zipline, a startup making drones that can deliver small packages like meals and medical supplies, is in talks to raise $1 billion at a valuation of roughly $20 billion, according to three people with knowledge of the fundraise.

The funding round, if it closes, would more than double its valuation from its last funding round, which valued the company at $7.6 billion after the investment. It follows a partnership announced last month with Uber to expand delivery by drones across the U.S. and expectations by investors that the costs of drone delivery are falling, expanding what was once a niche market.