:::::::It's still pointless. Classified by who exactly? That's the first problem. But even if you add 'by the ATSB', then you are assuming that the reader of the lede is familiar with ATSB terminology or already knows what the ATSB classes as a 'serious incident', or even that they want to know that at all, before they have digested the lede and decided they want to read the main article, which is where this sort of thing should be explained. You are helping nobody but yourselves by adding info to the lede that you already know the meaning of, but to the normal reader, is likely to be meaningless, and in an encyclopoedia which only has articles on serious incidents (supposedly), is completely redundant padding.