Look at all the pretty drones. Hovering above sports stadiums from Houston to Pyeongchang, many hundreds of them have lately sparkled in artful murmuration. On a recent Time magazine cover, 958 drones pixelated the sky. The world record, 1,374 LED-bedazzled microbots, was set by Chinese company EHang UAV in May. So-called drone swarms—the phrase people have taken up with gusto—are having their biggest, buzziest year ever.