How long would it take for six 767s to become operational and flying cargo for ATI? Can we expect these "early 2021" ?
Well, just FWIW, it's pretty-clear that at least one of the six and possibly two are going to go somewhere other than to Amazon, and maybe one of those will be going first to ATI as a spare and maybe later to Amazon. We shall see...which makes it fun!
But to answer your question about how fast IAI can turn out 6 conversions, the answer is between 5-6 months from the time the plane arrives, given what ATSG wants done to them. Just cutting and installing a cargo door can be done faster, but these aircraft basically get a heavy-check and the concurrent modifications to make them suitable freighters and to be flyable for another 20 years, as well as the cargo-door installation. IAI's second-line facility at Mexicana MRO in MEX has been converting aircraft for DHL (flown by Kalitta) in as fast as a little-less than 4 months, with the average about 4.25 months, but I'm not sure the scope of work is identical. The problem with the MEX operation is that they only do one aircraft at a time. So the plus is that all their attention is focused on it; the minus is they don't do stuff concurrently. ATSG gets its aircraft back unpainted from TLV; at MEX, I think they roll it somewhere there for paint. (Paint takes 2 weeks at ATSG's painting contractors.) Couple of other differences.
So figure that, from the time the aircraft arrives at TLV, roughly six months over there, then upon to return to the US a couple of weeks of conformity and such at AMES and two weeks in paint if it's going to be painted then. So good rule of thumb is 7 months give or take from arrival in TLV to earliest-possible in-service date.
I noticed that the most recently-delivered-to-ATSG conversion will be flown as a spare by ATI during Peak and maybe leased to Amazon next year, so rather than spend the two weeks in paint now, ATI will run it with the new metalwork having been painted grey over the green by IAI, and then send it for a full painting before it, say, goes to Amazon.
And, of course, things can be discovered during the heavy-check that require parts, paperwork, engineering, and/or approvals beyond the norm, and slow things down. One nice thing about the fleet of similar retired-AA 767-300s is that they are going to have been well-maintained and have excellent, complete, single-owner maintenance records kept under the same standards and protocols, which can help the whole process go faster. (And I am led to understand that sometimes when aircraft are owned, operated, and maintained in other countries, getting a clear, nuanced translation of what notations in other languages actually mean in technical terms can sometimes lead to conformity delays. So given that the AA aircraft were largely-maintained in Oklahoma their whole lives can eliminate that potential delay.)
Right now, the ATSG aircraft have been arriving in TLV at a pace of about 1 per month, give or take. Specifically, 3/31, 4/11, 5/31, 7/8, 8/20, 9/11. And in Israel, IAI can be working on something like 16 aircraft simultaneously at its facility (for MRO work and conversions). It's big. So figure that the aircraft that has been there longest from ATSG right now, N394AN, would under normal circumstances be getting ready right about now or in the next week or so to head back to the US, followed in order by the other ones.
Hope that helps!!