I have been studying history of relativity theory and now it seems to me, that it is wrong to automatically assume that proofs of Lorentz covariance are proofs of Special relativity theory. It seems to me, that there is broader group of theories, that are compatible with Lorentz covariance but are not compatible with Special relativity theory. You could divide these theories in two major group. One group is Special relativity theory and similar theories, which assume, that there is no preferred frame of reference. The second major group are theories who are consistent with Lorentz covariance, but are based on preferred frame of reference. Most known member of this group is Lorentz ether theory. I know, this is not a mainstream theory and the point is not to try promote Lorentz ether theory. The main point here is if this second group of theories with preferred frame of reference was never proved wrong that leads me to logical conlusion that experiments which are mentioned as proofs of Special relativity theory are actually not proofs of Special relativity, but only proofs of Lorentz covariance. But if Im right there is major simplification in learning and presenting of relativity theory which is simply not true, despite being the only mainstream view.