I think I've got the WWI part... Feel free to correct etc! Also, I wrote as I went, haven't checked it yet, going to finish the other part first.
I'm going to talk about aircraft.
I will start with World War 1, after that comes World War 2 in Europe, and I’ll end with World War 2 in the Pacific.
Before World War 1, planes were not used or designed for warfare. So when the war started, the planes were used for scouting, not combat. Because of the war people started carrying guns and bombs inside the planes, to shoot from the cockpit and throw bombs overboard. That was of course not very effective since it’s very inaccurate and the bombs were quite small. Later the onboard guns were exchanged for built-in guns. That presented some problems, for example, if you place the machine gun in front of the pilot, you could accidently hit the blades off your own aircraft, in which case you crash. Basically, they were not very effective at all, except for scouting. Kites and balloons were also used for scouting, which was cheaper. (pictures) There were also Zeppelins, which were essentially big airships that would slowly fly over cities for bombing raids. However, they could very easily be defeated with incendiary bullets.
Overall, aircraft were not very decisive in World War 1, especially in comparison to the weapons used on the ground.