With a sufficient number of drones in the air simultaneously, this becomes a far more difficult problem.

Birds are pretty dumb on average, and handle it really well.

Birds are not that dumb and compared to drones they're Einstein.

Specialized in flying, including eyes and brains, at that!

Autopiloted is much easier than cars because air space is less crowded with less obstacles and extremely well controlled. Low flying delivery drones don't fall in that bucket.

Less crowded now. But if they take over all those deliveries that are going on now the sky will get quite crowded and I suspect we will see people asking for no fly zones and for drones to be constrained to fly along roads instead of low over people's gardens. I certainly don't want hundreds of drones flying over my garden every day. Something like 35 million people in the UK buy something online every week, that would be a lot of drones. If you imagine that there is a distribution centre for every 50 000 people in the UK, that's roughly 1 500 distribution centres each with over 3 000 drone flights per day.

I realize that this is a very rough calculation and that of course there would be large variations in flight frequency but no one else seems to be showing anything better.

I don't think I would want to live near one.

With thousands of drones crossing the city sky, there would have to be some kind of system to organize that traffic, both to minimize collisions and sound pollution.

It's not hard to imagine how systems like that could be organized.

It's also important to consider how many road vehicle trips this would replace.

I don't care how it is organized, I just don't want them all flying over me. Living near such a distribution centre would be like living next to an airport unless there are regulations enforced that they ascend vertically so high that they cannot be heard.

How many road trips would it replace? Drones capable of carrying a 5 kg payload over any distance are fairly big. The DJI Matrice 600 Pro for instance weighs 15 kg and is over a metre across. It has a hover time of only 18 minutes. Maximum speed is 65 kph so its round trip range is about 20 km.

A small electric van can easily carry a hundred such packages and has an empty weight of roughly one hundred times that of the drone.

Presumably the drones used for deliveries would have to be much more robust and have much longer ranges, both of which would make them heavier.

So 100 drones replace one van.

I'm sure there are huge holes in my analysis perhaps, you can improve it so that it shows that a substantial number of road trips would be replaced without filling the sky with drones.

Birds aren't real. Google it, "do your own research"!

Only on places where they concentrate. It's not really flying that is difficult, it's approach and take-off, because they have to go through all of the heights.

Big sky theory falls apart near airports already, and a crowded drone filled sky would have issues especially with unexpected weather.

Anyway, I guess the main problem is that most people will not want a sky full of drones just so that some random Joes can get their stuff from Amazon or AliExpress a little sooner.

If the skies fill with drones while traffic jams ease, there’s less double parking for delivery, and streets generally start looking more airy, people may make the association.

That's not going to happen. Check out "induced demand".

Otherwise as selling dollara for dimes. At least in the last VC bavked iteration of it.

This time it's different because we know where it might lead to.

Historically speaking, tech is relatively unregulated and protocols are all over the place. I'd say it's a safe assumption.