There are a variety of aerial download sources that can be found by a web search. I'd try a Google search on "aerial downloads" and "orthophotos". If you want a specific geography instead of the whole world, I would add in search terms related to that geography. For example, "aerial downloads United States".
Another avenue to search is government agencies, as often they are providers of imagery.
Here's a few of the many results a quick search revealed.
USGS Earth Explorer
https://libraries.mit.edu/files/gis/earthexplorer.pdf
EarthExplorer
NCSU Digital Aerial Imagery and Orthophotographs
Digital Aerial Imagery and Orthophotographs :GIS: NCSU Libraries
Chris Donohue, GISP