Before you do anything, ask your friend this: "Why do you want to place the airplane into an LLC?"
The answer matters.
Many people labor under the misapprehension that, if an aircraft is in a corporate entity (Corporation, LLC, Ltd. partnership, whatever), that the owner is then shielded from liability. This can work (on a limited basis) if you have multiple owners, each of whom is a member of the LLC, and one of them does something bad with your plan, which could serve to protect the other owners from worse liability.
Of course, the best protection from liability is a rocksolid insurance program and, of course, safe operational practices.
Some people think that they can avoid tax in their home state, by placing the aircraft in an LLC or corporation which is native to another state. This is was known as "silly talk, and might or might not work for a while, until you get caught, whereupon you pay everything you would paid anyway, together with substantial interest and penalty.
Of course, if you ever think about the legal expense of maintaining a corporate entity, or the fact that they have another of reporting entity for tax purposes.