On October 21, Sweden’s Jetson Aero launched the Jetson One, a single-seat flying car with 20-minute flight times and a top speed of about 63 mph. It has already sold all 12 of the electric vehicles in its first production run (to be delivered in fall 2022), and it’s now taking orders for 2023.

The vehicles will be delivered about 50% assembled, and customers must finish putting them together themselves.

More than 150 companies are developing flying cars. Here’s why they’re aren’t yet off the ground and darting across city skies.