After working on Prime Air for ten years, Amazon is still grappling with the cost structure of using autonomous drones to drop packages on customers’ doorsteps within an hour.

Internal projections viewed by Insider predict each drone delivery to cost $63 per package in 2025, the year Amazon aims to deliver one million packages annually by drone.

Amazon’s current on-the-ground per package delivery cost is estimated to be less than $5.50.

The tech giant has been quietly testing Prime Air deliveries in a handful of rural areas in Oregon and California for the past 18 months and is looking to expand the trial test to 1,300 shoppers later this year.

By 2025, the documents project that Prime Air will be offered in 32 different locations.