The Warning Letter is what I referred to, and it does exactly what I claim. I can attest to that personally; for investigations that resulted in no action, a warning letter placed in the file states that no evidence was found of wrong doing, and then goes on to state that doing XXX is a violation of 14 CFR XXX. The employer, or future employer who asks if one has had enforcement action or received a warning letter may not ever read the letter (which states insufficient evidence found to proceed with enforcement. The warning letter, however, has a damaging effect on the career of the airman; in the past, these were supposed to be removed after two years, and this was very frequently not done. Moreover, I can personally attest to employers in PRIA checks receiving not only the warning letter on file, but also a letter of investigation, because I have had new employers tell me about them after receiving my FAA information. I realize the FAA states that this doesn't happen, and that the LOI is a local affair; real-world experience (you can dismiss as anecdotal, if you wish) has proven otherwise.

In short, Iv'e seen both show up in the airman's record.

During the kinder, gentler FAA phase, I've not found that to be the case among inspectors who work in a field where one of the application requirements is that the applicant cannot have had more than two aircraft accidents in the prior five years, for which the applicant as at fault. My respect level for inspectors and their knowledge and understanding of the regulation and associated process is low; the FAA sets the bar low, and it shows. It's for that reason that I was able to have two LOI's and warning letters. One of those I received after a call from an inspector in the LAS FSDO a number of years ago, who told me he wanted evidence to use against my employer; he told me that if I would obtain the records and files from the employer and provide them to the inspector, he would table the matter, because he knew it had no merit (company records showed 1/2 hour too little rest on one date; it was a clerical error and it was obvious. I refused to spy on the employer or steal records. Subsequently, I received a letter of investigation, and. later a warning letter in my file stating that while the FAA could find no evidence of wrong doing, it was wrong of me to do it. Another event involved the head of a FSDO that called me into his office and told me to buy his secretary a dozen red roses, or he'd find a reason to violate me. I kid not. One can't make that **** up.