I agree with Enplaned. Usually, of course, Prime Day comes at a generally-slower time of year.
My observation in past years is that Amazon, unlike most consolidators, has frozen the expansion of its network prior to Peak, focusing on smoothness of operation of the existing setup rather than trying to bump up right at Peak. That kind of bumping up can lead to all sorts of disruption and confusion, which they plainly wanted to avoid in the past. Perhaps this year or in the future, they may change that strategy, but if I had to bet, I would believe that they will just fill the planes as much as they can and kick the rest to other channels. I have read over and over how Amazon's computers calculate in advance to a remarkable degree of precision what to send to the Air network so that they just-fill but don't overfill the cans and the planes.
Amazon for sure has the necessary info to do that - I know for a fact, however, that three years ago they did not do this. I would hope that in the intervening period they would have leveraged this, because it's a potentially huge advantage over UPS, etc.
The real advantage is in knowing, say, at the far end, how many trucks to show up with to go to sort center A, delivery station B, etc. You should be able to get there with exactly the right number, essentially all the time.
It's not that they calculate it in the sense of some kind of slick probability. It's that the minute a package goes through SLAM (receives its label, which includes, inter alia, the path that it will follow) you know how, from now through when the package is delivered, its intended route. So you know to a fairly near certainty what that package is going to do (leaving aside the issue of misrouted/lost packages or a cancelled flight). So, you know that some hours in the future, that package is coming off an aircraft in, say, ABE and it will need get to, say, a Philly-area sort center or delivery station for onward sortation/delivery. So you can add up all the packages, their size, weight, etc, that will be getting off that ABE flight and going to that Philly-area delivery station - and now you know whether it's one truck or more.
UPS can't do that, neither can Fedex.