I have a Nikon G-Canon Eos adapter that means i can use all nikon mount glass on my canon bodies, even the newer AFS-G units that no longer have the manual aperture ring. As well as this i also have a Zeiss-Eos adapter and an M42-Eos adapter.
If you are going to do this be very careful as some different lenses can cause the mirror to hit protruding elements on some lenses. For example i can use most lenses on my 400D/10D and 1d2 with the adapter but on my 5D2 i have to be more careful as it has the larger mirror due to the full frame sensor. While it's not something I've really dabbled in much the possibilities are very good. There are a lot of photographers who are using the Nikon 14-24F2.8 on Canon bodies for mainly landscape photography as it is a much better performer than the Canon 17-40/16-35.
For aviation it isn't really going to help you as you rely on autofocus for these shots, that is something you lose when you use mount adapters. For other purposes like Macro/Landscape/Portraiture it can work very well.
5D2/7D/1D2(soon to be a 1Dx) 17-40L/24-105L/70-200F2.8L/100-400L/24F1.4LII/50F1.2L/85F1.2LII