I switched from Canon full frame to m4/3 fully about 10 months ago.
With regard to aviation photography, probably the biggest weakness is continuous focus. Obviously for static shots this won't matter, and you're probably
OK with airliners on approach, but in general, fast jets coming towards you and the like, forget it. The possible exception to this is the EM-1 with latest firmware - while not as good as, say a 7DmkII it is pretty decent and should cope with most situations.
In terms of image quality, I really like the Oly sensors compared to Canon. Colour is better, and so is the dynamic range. However if you regularly shoot above 1600 ISO, you may not be so happy.
Probably the biggest thing to get used to is the switch from optical to electronic viewfinder. While getting better all the time, EVFs don't match a good OVF optically, BUT there are a lot of advantages, particularly exposure as what you see is what you get, and you can overlay histograms or blinkies - getting super accurate exposure everytime goes a long way to optimising image quality. Also, many models have a "focus peaking" feature. This makes manual focus a practical alternative to
AF.
Lenses - like DSLRs there is great glass and not so great. In general you get what you pay for, but there is a huge choice at all price ranges for mFT.
In summary, I have no regrets switching, I'm definitely now getting more keepers and better
IQ overall YMMV
Cheers,
Colin