Think of the liability when on eventually crashes. These are supposed to be near where people live since the drones will be delivering goods from them.
https://www.cnbc.com/2016/12/29/amazon-flying-warehouse-deploy-delivery-drones-patent.html
Amazon wins patent for a flying warehouse that will deploy drones to deliver parcels in minutes
Arjun Kharpal | @ArjunKharpal
Published 7:04 AM ET Thu, 29 Dec 2016
I am sure they would do their best to ensure the utmost in safety but I can imagine something like a product with lithium batteries exploding, sabotage from a disgruntled vendor/employee or terrorism causing it to catastrophically break up at altitude without warning, raining down thousands of pre-packaged flaming missiles and drone parts on an unsuspecting heavily populated urban metropolis.
Could mean some lawsuits.
My son just pointed out that many warehouses are reluctant to stack pallets on racks more than five high, 40K feet is out of the question.
Unrelated butt: I had an experience at a previous job where one of the logistics hubs fell way( and I am talking way) behind. Management went insane scrambling to get freight moved through the system. They were flying in (even semi) experienced lift truck drivers some just for a few hours to fill all of the shifts. They had the wrong size forks for their fork lifts and the drivers would accidentally push the pallets on the other side of the rack, off the top this was a huge warehouse and there would be a crash with pallets exploding on the floor almost every two minutes. I kept my eyes to the skies walking thru there.