There is PLENTY of Amazon volume to go around.

I'd also guess that margins on Amazon parcels are pretty low for that reason.

It makes good business sense for Amazon to diversify their delivery vendors and to seek lower delivery costs. If they can spin up their own air delivery service using ATSG and accomplish both objectives then good for them - but I don't see them going away from third-party shippers for bulk movement and home delivery any year soon and I certainly don't see them challenging third-party shippers for outside business. Package delivery isn't web/cloud hosting - it is MUCH more capital/labor/regulation intensive and a far stretch from Amazon's core businesses.

But I've been wrong before...