YMC has been covered a lot here, and this is a subject that is a fine line between right and wrong. Normally the classic N-1 issued USN deck jacket rests on a 100% cotton, either waxed or not. YMC took that and did a leather version which I actually think works pretty well.
The same way the N-1 is cotton, the A-1 or G-1 flight jacket is mostly leather. It’s nice to mix the different fabrics up with the different issued garments. The real shearling and throat latch are must-haves as well. Overall, I think they hit it spot on.