Some link to third party website that holds Boeing or Airbus presentation becomes dead. I have no hope to bring back those link to life. Should I edit to remove those dead links or should I just leave it there?
Ideally you would find a new source of the same information and edit that in, but failing that it might be better to remove the link or indicate it is now dead.
Incidentally, this is why we prefer the relevant information to be quoted in an answer alongside the link, rather than just include a link.
Personally, I agree with Notts90's comment. While I think adding some text to note that the link is dead is fine if you can't quickly find a replacement, I think just removing outright is harmful.
Perhaps someone else will find another source for the resource if they see the link is dead, whereas it will likely never be fixed if you just remove it. For example, someone might find an archived version of the original link on the Wayback Machine. Changing the link to that would be much more useful than simply removing it.
And, of course, as Jamiec notes, it would also be ideal to quote relevant information in the answer body itself rather than having only the link.