1. One presumes that back in the day, it was difficult to produce cloth of a tight enough weave to protect from wind while being warm and durable. Hence leather. Also, leather doesn't burn very well.
These same attributes also apply to the flight jacket as an everyday wear item and for driving. However, the elastic waistband design is not suitable for motorcycling.
2. Loyalty forces me to choose the G1. Moreover, it has a functional inside pocket, a bi-swing back, and quieter patch pocket buttons. Plus a pen pocket. The A2 provides a sleeker profile, but is nowhere near as functional. But the horshide looks better, even if it isn't as durable as goatskin.
I and my A-2 have a funny story to tell. I once wore it shopping, and while entering Nieman's I was confronted by one of several animal rights types picketing the store. He asked "do you know what some cow went through so you could have that jacket?" or some such. I turned toward him and his friends, looked him straight in the eye, and replied, "this jacket is made from horsehide," and entered the store.
3. My absolute favorite is the RAF Irvin sheepskin jacket from WW2. Has "Hero" written all over it, very warm, and since it's belted, it's safe to use as a motorcycle jacket. Drawback? No pockets...
4. The WW2 version of the G1 is the M422A. Flight Suits and Eastman make excellent reproductions.
5. A summer Nomex CWU is lighter, safer and far more functional than any leather jacket. But it looks terrible and is difficult to keep clean in a military aviation environment.
