You can no longer download a single, large, skin file with all skins.
I suspect (I don't know) that it's because every time they upgrade a new plane it's that much more work to recompile the 100+ MB file. It's much simpler to host each file individually (for HTC's part).
That being said, I'd just bite the bullet and download 'em all!
Or just enable skin downloads in the hangar whilst online, and give it time.