Fly while in Uganda:
There are services like Aero Link which flies to National parks and places mainly for tourists. Once you are in a park with them, you have to fly back to Entebbe to get to another park.
There also charter services that will take you in between parks. Lower priced services are like Eagle Air and Mission Aviation Fellowship that will take you to towns and places at more reasonable price. However, most of those towns are not located near tourist Spots. Flying in Uganda is quite safe and reliable and there have been no crashes reported. The planes are well-maintained and have excellent Pilots.