This weekend Amazon Chief Executive Officer Jeff Bezos told 60 Minutes that he wants small unmanned aerial vehicles — drones — to speed packages to online shoppers as early as 2017, cutting delivery times to as quick as 30 minutes.

It’s a bold, imaginative plan — one that could propel a host of technological and legal advancements.

It’s also really, really difficult to pull off. What follows are just four of the reasons Bezos’ Amazon delivery-drones might not get off the ground.

1)  Drone delivery flights are illegal, at present. Among other prohibitions, the Federal Aviation Administration bans drone flights over 400 feet altitude and near airports and populated areas. Bezos’ plan is for the robots to take off from fulfillment centers near big cities. They might be able to stay below 400 feet and avoid airports. But exactly how can a drone deliver a package to a populated area without flying over … a populated area?

More important, the FAA currently bans all commercial uses of drones. Simply stated, you’re not allowed to make money off them — which is exactly what Bezos aims to do.