Level III contractors: which form of business?

I'm having no luck finding mentorship so I'm just going to go ahead and start a Level III consulting and contracting gig. For those of you who have done so, which form of business did you choose? Should I go with a sole proprietorship or an LLC? Presumably I may be buying off parts and signing reports, so I'm thinking LLC might be smartest.

For the record, I have 15 years of aerospace NDT (RT, DR, CT, and PT) in the US.

If any of you would like to guide me, please e-mail me at gabriel.balensiefer@gmail.com

Thanks in advance.