Why would China rely on something as low-tech as a weather balloon to spy on the United States and other countries?

Well, compared to satellites, balloons are cheap. And a balloon can observe an area for a long time because it’s in sync with the earth’s rotation, says Vox producer Coleman Lowndes.

In addition, the Biden administration said Thursday that the Chinese balloon shot down by the United States was equipped to detect and collect intelligence signals. China, according to the White House, has a fleet of balloons outfitted with high-tech equipment designed to spy on 40 countries.

Meanwhile, China is sticking to its story: The balloon was simply a civilian meteorological airship that blew off course.

Watch: Why Does China Still Use Spy Balloons?