I recently found some information that addresses this issue (whether to form an LLC) directly. I will copy my email to a fellow VAF member verbatim rather than trying to retype it:
Okay, here is what I?ve found out? This is from an aviation attorney whose name escapes me right now. Rex Reese or something like that.
Most guys who are titling the plane under an LLC or corporation for the purpose of mitigating liability are actually doing themselves a huge disservice and might be increasing their liability. The reason is that when a company owns and operates an airplane, it is acting as a ?corporate flight department? (or something like that) under the FARs. A corporate flight department generally operates under the loose requirements of Part 91 when it is operating the aircraft for its own business purposes. One requirement of Part 91 is that the flight department not be compensated for flights by passengers.
When you form an LLC and inject capital into it (for maintenance, hangar fees, operating expenses, insurance, etc.), the FAA considers that compensation. The LLC is essentially acting as a charter or on-demand operator and both the pilot and the aircraft are subject to Part 135. That means commercial pilot?s license, flight time restrictions and more vigorous inspections, not to mention that a homebuilt can?t be operated under part 135 (I don?t think). It doesn?t matter that you, acting as the company ?owner? are the only one in the plane. You, acting as the company pilot, are carrying yourself as a paying passenger (remember that you and the company are separate legal entities). If you aren?t operating under Part 135, you are operating illegally and in a manner that is de facto negligent. If you wreck and hurt someone, this fact makes a plaintiff?s case that much more airtight.
A seemingly plausible workaround is to have the LLC lease the airplane to you, personally, as the operator. But then you?ve lost the protection you sought by forming the LLC, so it?s pointless.
Hope this makes sense. This is definitely a question for an aviation attorney & I ain?t one?