Wow.
A timeline on what was set to be the biggest invasion ever, something that would make Normandy look like a scouting jamboree, for your FIRST effort.
Wow.
There are tons of sources available on Downfall. I would suggest the U.S. Strategic Bombing Survey, Pacific Theater as an excellent resource regarding both the American & Allied airforces that were going to be in the region to support the assault as well as a very credible, well documented, series of interrogations/interviews with surviving Japanese officers who had planning responsibilities. There is also a very good listing on IJN & IJA aircraft inventories in the same set of documents.
There are several sites with the survey online, as well as others with just the summary. I would suggest looking at the full report, assuming you have the time.